High figure-of-merit in the heavy-fermion UN₂ system for radioisotope thermoelectric applications

The design of uranium-based thermoelectric (TE) materials presents a novel and intriguing strategy for directly converting nuclear heat into electrical power. Using high-level first-principles approach combined with accurate solution of Boltzmann transport equation, we demonstrate that a giant n-type power factor of 13.8 mW m^-1 K^-2 and a peak ZT value of 2.2 can be realized in the heavy-fermion UN₂ compound at 700 K. Such promising TE performance arises from the large degeneracy (N _v = 14) of heavy conduction band coupled with weak electron-phonon interactions, which is in principle governed by the strong Coulomb correlation among the partially filled U-5f electrons in the face-centered cubic structure. Collectively, our theoretical work suggests that the energetic UN₂ could serve as both excellent heat source and efficient power convertor, which also uncovers an underexplored area for TE research.