Stagaire ou Alternant(e) RH
Your mission
As an HR Intern at Mantle8, you will play a key role in structuring and operating our HR function in a fast‑scaling environment.
This is not a “classic HR internship”.
You will contribute both to:
- building solid HR foundations
- ensuring day‑to‑day HR operations run smoothly
What you will do
- HR structuring & digitalization
- Improve and structure our HRIS (Lucca)
- Organize HR documentation and workflows
- Contribute to the digitalization of HR processes
- Create clear and useful internal guides for employees
- Employee experience & HR content
- Support onboarding processes
- Help formalize internal policies (working time, remote work, leave)
- Contribute to our internal HR knowledge base ("Bedrock")
- HR Operations & People administration (core part of the role)
- Employee lifecycle management
- Draft and follow‑up contracts, amendments, and HR documents
- Manage administrative files
- Payroll coordination (France)
- Prepare monthly variable payroll elements (EVP)
- Interface with external payroll provider
- Ensure data accuracy and reliability
- International HR coordination (remote employees)
- Work with foreign partners (UK, Germany, Sweden…) for payroll & admin
- Support cross‑border HR structuring
- Gain exposure to international HR practices
- Interns & trainees administration
- Manage internship agreements
- Coordinate with schools and institutions
- A real HR relay
- Take ownership of topics with increasing autonomy
- Interact with employees and external partners
- Actively contribute to structuring the HR function
You will gain a 360° understanding of HR operations, in both French and international contexts.
Profile required
About you
- Curious, structured and proactive
- Comfortable with digital tools and eager to optimize processes
- Fluent in English (daily working language)
- Fluent in French to work in French (HR documentation & compliance)
And who is interested in
- HR structuring & digitalization
- Fast‑growing environments
- Meaningful, science‑driven projects
Why join us?
- Work on real HR topics with real impact
- Gain exposure to international HR operations
- Be part of a fast‑growing deeptech startup
- Contribute to an energy transition project
- Join a diverse, collaborative and science‑driven team
- Work in Grenoble, at the heart of the Alps
Final note
This internship is a unique opportunity to develop a dual skillset: structuring HR foundations and running day‑to‑day HR operations.
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.
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 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.
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