  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,
Ce$_3$Bi$_4$Ni$_3$. It is an isoelectronic analog of the prototypical Kondo
insulator Ce$_3$Bi$_4$Pt$_3$ and of the recently discovered Weyl-Kondo
semimetal Ce$_3$Bi$_4$Pd$_3$. In contrast to the volume-preserving Pt-Pd
substitution, structural and chemical analyses reveal a positive chemical
pressure effect in Ce$_3$Bi$_4$Ni$_3$ 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 Ce$_3$Bi$_4$Pt$_3$ and about
45 times larger than that of the Kondo-insulating background hosting the Weyl
nodes in Ce$_3$Bi$_4$Pd$_3$. We show that this gap as well as other physical
properties do not evolve monotonically with increasing atomic number, i.e., in
the sequence Ce$_3$Bi$_4$Ni$_3$-Ce$_3$Bi$_4$Pd$_3$-Ce$_3$Bi$_4$Pt$_3$, but
instead with increasing partial electronic density of states of the $d$
orbitals at the Fermi energy. To understand under which condition topological
states form in these materials is a topic for future studies.
