Job description
What the role is about
As Financial Controller, you'll join Mantle8's finance function and own financial planning and management control (FP&A / contrôle de gestion) across the TopCo and our project entities (SPVs) — supporting our growth, our fundraising cycles, and our industrial/exploration projects.
You'll work closely with our current Funding Manager, and with an incoming Finance Director (DAF) as the team scales — the exact split of responsibilities will be shaped around each person's strengths. Day-to-day bookkeeping, payment execution, and bank reconciliations are handled by our external accounting firm; your role is to own the budget, forecasting, and analysis, and to be the primary point of contact with that firm to ensure reliable, timely financial data.
The role requires the analytical rigour of a controller, the operational discipline to close the books on time every month, and an entrepreneurial mindset — comfortable rolling up your sleeves in a lean, fast-growing team.
What you'll be doing :
- Build the annual budget and recurring reforecasts for the TopCo and SPVs; produce budget vs actuals analyses.
- Develop cash-flow forecasts and runway projections; communicate cash/runway views to the executive team and to investors.
- Monitor bank account positions and treasury flows; coordinate with the external accounting firm on payment execution, reconciliations, and the monthly close calendar.
- Track analytical accounting by project, department, and technology.
- Prepare financial data and documentation for CIR (Crédit Impôt Recherche) and grant/subsidy applications.
- Deploy and improve financial tools and reporting (including Power BI dashboards); structure expense-commitment workflows.
- Act as the interface between the external accounting firm and operational teams.
- Support fundraising processes and investor reporting alongside the Funding Manager.
Partner with the incoming Finance Director (DAF) to help structure and scale the finance function.
What we offer :
- Corporate welfare plan & supplementary health insurance
- Indefinite contract (CDI) with full French employment protections
- A meaningful role building a new clean, affordable, sovereign energy source
- High-exposure role at the financial core of a fast-growing clean-tech start-up, direct interface with the CFO, COO, and all functions
- Collaborative, dynamic, diverse work environment in the stunning French Alps
Profile required
Essential :
- Solid experience (generally 5+ years) in FP&A and management control — exceptional candidates with less experience may be considered if English is fully fluent and the profile is otherwise an excellent match
- Experience building annual budgets and reforecasts in a multi-entity context (TopCo + SPVs)
- Experience producing budget vs actuals analyses
- Experience with cash-flow forecasting and runway projection
- Experience monitoring treasury/bank positions and coordinating with accounting/banking partners
- Experience driving or coordinating a monthly close process
- Fluent English, oral and written — our day-to-day internal communication (including with international investors) is largely in English
- Professional French, for interfacing with our external accounting firm and French administrative/tax bodies (CIR, URSSAF, etc.)
Highly valued :
- Experience preparing financial data for CIR and grant/subsidy applications
- Experience with analytical accounting across multiple axes (project/department/technology)
- Experience deploying or improving financial tools (Power BI in particular) in a startup or scale-up environment
- Experience structuring expense-commitment workflows
- Experience interfacing with external accountants and operational teams
- Prior experience in a high-growth startup or scale-up environment
Company description
🇬🇧 Mantle8 is a deep-tech exploration company dedicated to unlocking the potential of natural hydrogen as a new clean energy resource.
By combining advanced geoscience, subsurface modeling and cutting-edge simulation technologies, Mantle8 develops innovative exploration methods to identify and evaluate natural hydrogen systems deep within the Earth.
Our multidisciplinary team brings together geoscientists, engineers, data scientists and explorers who share a common ambition: advancing scientific understanding while building the foundations of a new energy frontier.
From regional exploration concepts to prospect generation and technological development, Mantle8 works at the intersection of research, innovation and industrial application to accelerate the emergence of natural hydrogen as part of the global energy transition.
At Mantle8, exploration is not only about discovering new resources — it is about expanding knowledge, challenging assumptions and building solutions for the future of energy.
Why is everything in English if Mantle8 is based in the heart of the French Alps?
Because Mantle8 is an international adventure.
As of March 2026, our team includes 21 people representing 9 different nationalities. This diversity is one of our greatest strengths, and English is the language that allows everyone to collaborate, debate ideas and build things together.
We love our home in the French Alps, but inside Mantle8 our common ground is English — from meetings and technical discussions to emails and, yes, even our jokes.
So if you’re thinking about joining us, English is not just helpful — it’s essential to be part of the conversation.
🇫🇷 À propos de Mantle8
Mantle8 est une entreprise deep-tech d’exploration dédiée à révéler le potentiel de l’hydrogène naturel comme nouvelle ressource d’énergie propre.
En combinant géosciences avancées, modélisation du sous-sol et technologies de simulation de pointe, Mantle8 développe des méthodes d’exploration innovantes permettant d’identifier et d’évaluer les systèmes d’hydrogène naturel présents en profondeur dans la Terre.
Notre équipe pluridisciplinaire réunit géoscientifiques, ingénieurs, data scientists et explorateurs partageant une ambition commune : faire progresser la connaissance scientifique tout en construisant les bases d’une nouvelle frontière énergétique.
De la génération de concepts d’exploration régionaux à l’identification de prospects et au développement technologique, Mantle8 opère à l’interface entre recherche, innovation et application industrielle afin d’accélérer l’émergence de l’hydrogène naturel dans la transition énergétique mondiale.
Chez Mantle8, l’exploration ne consiste pas seulement à découvrir de nouvelles ressources — il s’agit aussi d’élargir la connaissance, de remettre en question les certitudes et de construire des solutions pour l’énergie de demain.
Pourquoi tout est-il en anglais alors que Mantle8 est basée au cœur des Alpes françaises ?
Parce que Mantle8 est avant tout une aventure internationale.
Début mars 2026, notre équipe compte 21 personnes représentant 9 nationalités différentes. Cette diversité est l’une de nos plus grandes forces, et l’anglais est la langue qui nous permet de collaborer, de débattre d’idées et de construire ensemble.
Nous sommes très attachés à notre ancrage dans les Alpes françaises, mais chez Mantle8 notre langue commune est l’anglais — que ce soit pour les réunions, les discussions techniques, les e-mails et, oui, même nos blagues.
Donc si vous envisagez de nous rejoindre, l’anglais n’est pas seulement utile : il est essentiel pour faire partie de l’aventure.
On 8/19/2026