  The axion is an hypothetical beyond the Standard Model particle. Its
experimental search is an ongoing effort, and an expanding number of techniques
keep on narrowing its parameters space. Leveraging the interaction between dark
matter axions and spins, a fermionic interferometer is an experiment which aims
at detecting the axion-induced precession of a spin resonance. We describe the
detection scheme, outline the possible experimental implementations, their
sensitive axion-mass range and discovery potential. Furthermore, the building
and characterisation of an axion interferometer is explained in details and the
resulting setup is used to search for sub-neV dark matter.
