SUPERCONDUCTIVITY IN Y-NI-B BASE COMPOUNDS

Carbon introduced in Y-Ni-B ternary alloy material was shown to stabil ise a quaternary compound YNi2B2C which is also responsible for the ap pearance of superconductivity in Y-Ni-B alloys YNi4-xB1+x. Rietveld re finement of a nearly single-phase material of YNi2B2C confirmed isotyp ism with the filled ThCr2Si2-type (z(B) = 0.353(1)). Magnetic and spec ific heat measurements indicate type-II superconductivity in YNi2B2C w ith a T(c-onset) of 15.2 K and a normalised specific heat discontinuit y DELTAC/gammaT(c) = 1.57. We present a first estimate of the upper cr itical field mu0H(c2)(0) = 3.7 T, the coherence length xi(GL) 9.4 nm a nd the Ginzburg-Landau parameter K = 10.5 of this new compound.