Ce₃Bi₄Ni₃ - A large hybridization-gap variant of Ce₃Bi₄Pt₃

Abstract

The family of cubic noncentrosymmetric 3-4-3 compounds has become a fertile ground for the discovery of novel correlated metallic and insulating phases. Here, we report the synthesis of a new heavy fermion compound, Ce₃Bi₄Ni₃. It is an isoelectronic analog of the prototypical Kondo insulator Ce₃Bi₄Pt₃ and of the recently discovered Weyl-Kondo semimetal Ce₃Bi₄Pd₃. In contrast to the volume-preserving Pt-Pd substitution, structural and chemical analyses reveal a positive chemical pressure effect in Ce₃Bi4Ni₃ relative to its heavier counterparts. Based on the results of electrical resistivity, Hall effect, magnetic susceptibility, and specific heat measurements, we identify an energy gap of 65-70 meV, about eight times larger than that in Ce₃Bi₄Pt₃ and about 45 times larger than that of the Kondo-insulating background hosting the Weyl nodes in Ce₃Bi₄Pd₃. We show that this gap as well as other physical properties do not evolve monotonically with increasing atomic number, i.e., in the sequence Ce₃Bi₄Ni₃-Ce₃Bi₄Pd₃-Ce₃Bi₄Pt₃, but instead with increasing partial electronic density of states of the d orbitals at the Fermi energy. This work opens the possibility to investigate the conditions under which topological states develop in this series of strongly correlated 3-4-3 materials.