Abstract:
We have determined upper critical field, H-c2(T), from resistivity measurements in the borocarbide superconductors, RNi(2)B(2)C (R=Y, Ho, Er, Tm). The H-c2(T) of these materials show a positive curvature which is unlike of a conventional type-II superconductor. Features corresponding to coexistence of superconductivity and magnetism are observed in HoNi2B2C and ErNi2B2C. From the resistivity measurements, we observe a double reentrant behaviour in our sample of HoNi2B2C.