COMPOSITION DEPENDENT MAGNETORESISTIVITY STUDIES ON HONI2B2C

We report on resistivity measurements under applied magnetic fields up to 20 kOe on several HoNi2B2C samples with different phase compositio n. The results reveal the occurrence of three distinct states: a re-en trant superconducting state; a state where superconductivity and magne tism coexist and a non-superconducting magnetic state, all within the homogeneity range of the compound. The upper critical field curves sho w a non-monotonic behaviour, reflecting the influence of the antiferro magnetic and spiral magnetic transitions between 5 and 6.5 K and are a lso dependent on phase composition. The results are qualitatively disc ussed in the framework of multiple pairbreaking theory.