LUNI2B2C - A NOVEL NI-BASED STRONG-COUPLING SUPERCONDUCTOR

The surprising recent discovery of superconductivity up to T(c)=23 K in Ni- and Pd-based rare-earth borocarbides raises the question of whether or not these materials constitute a new class of high temperature superconductors (HTS). For LuNi2B2C, with T(c)=16.6 K and a (known) layered crystal structure I4/mmm, electronic structure calculations indicate that it is a strongly 3D metal with all atoms contributing to the metallic character, completely unlike the cuprate HTS. Incorporating resistivity data we deduce a very strong electron-phonon coupling lambda(tr)=2.6, which we relate to an unusual combination of states at the Fermi level and substantial contributions from the vibrations of the light atoms.