Borocarbide superconductors: Materials and physical properties

An overview is given on materials and physical properties of the borocarbide intermetallic superconductors, RETM₂B₂C (RE = rare-earth, TM = Ni, Pd, Pt). Extensive studies on Lu(Y)Ni₂B₂C have revealed that the compound is a three-dimensional and clean limit type II superconductor with a moderately high density of states at the Fermi level. The high density of states originates from the presence of a narrow d band near the Fermi level. Intermediate coupling with phonons and the high density of states are likely to account for the observed high transition temperature. The presence of the narrow d band, on the other hand, results in substantial electron correlation effects.