SUPERCONDUCTING PROPERTIES OF THE NEW BORIDE-CARBIDE SUPERCONDUCTORS

The upper critical field H(c2) and the lower critical field H(c1) have been measured for a new family of boride-carbide superconductors, LnN i2B2C (Ln = Lu and Y) and mixed-phase Y-Pd-B-C. The results for the Ni compounds indicate that these are clean-limit superconductors with a coherence length xi of approximately 60 angstrom. A moderately high de nsity of states, likely due to a dominant Ni 3d character near the Fer mi level, is estimated from the obtained superconducting parameters, p lacing them in a comparable position to A-15 compounds in the linear s pecific-heat coefficient gamma and T(c) plot.