Electronic structure of the new MgCNi$_3$ superconductor and related intermetallic compounds

The band structure of the new perovskite-like MgCNi$_3$ superconductor is studied by the self-consistent FP-LMTO method. The superconducting properties of MgCNi$_3$ are associated with the occurrence of an intense peak in the density of Ni$3d$ states at the Fermi level. The absence of superconductivity for nonstoichiometric MgC$_{1-x}$Ni$_3$ compositions is caused by the transition of the system to a magnetic state. The possibilities of finding superconductivity for ScBNi$_3$, InBNi$_3$, MgCCo$_3$, and MgCCu$_3$ isostructural with MgCNi$_3$ are discussed.