FIELD AND TEMPERATURE-DEPENDENT TRANSPORT AND MAGNETIC-PROPERTIES OF SUPERCONDUCTING YNI2B2C

We present measurements of the AC susceptibility (at various frequenci es) and the field and temperature dependence of both the magnetisation and resistivity of YNi2B2C. These data, supplemented by X-ray measure ments, were collected primarily on samples produced by a chill-casting technique. Following annealing these samples display a slightly depre ssed T-c, but a considerably enhanced M(IRR) (and hence j(c)), H-cl, a nd, to a lesser extent, H-c2. Preliminary data on unannealed specimens indicate that this enhancement accompanies the annealing stage, thus suggesting a possibly subtle role played by the defect structure.