Electronic structure of superconducting LuNi2B2C, YPd2B2C and related intermetallic compounds

From first principles self-consistent band-structure calculations of the quaternary intermetallic compounds LuNi₂B₂C and YPd₂B₂C and of the related compound LuNiBC, we suggest that the superconductivity of the two former systems is related to the presence of a narrow peak in the density of states at the Fermi level, with mixed Lu(Y) d and Ni(Pd) d character. The strongly mixed character of these states results in a 200 meV large exchange splitting of this peak for ferromagnetically (F) aligned GdNi₂B₂C, implying that superconductivity is not expected to be present in the case of F alignment of rare-earth moments on Lu or Y sites. Based on calculations for some chemically modified compounds, experiments are suggested for testing the predicted shape of the DOS near the Fermi level.