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.