Hybridization and bonding in transition metal compound superconductors: X-ray photoemission from crystalline and amorphous Nb₃Ge.

An XPS (or ESCA) study of the high Tc crystalline and the low Tc amorphous phases of Nb3Ge indicates a change of the Nb-Ge bonding from covalent to metallic upon the amorphous to crystalline transition. The high Tc superconductivity of Nb3Ge does not appear to stem only from an unusually high electronic density of states at the Fermi level but rather from another property such as a resonant enhancement of the electron-phonon coupling resulting from cation-anion hybridization at EF. © 1977.