Precursor diamagnetism above the bulk transition in YNi2B2C

High-resolution SQUID magnetization measurements in YNi2B2C single crystal are used to derive insights on precursor phenomena approaching the bulk superconducting transition. The precursor diamagnetism is much stronger than the conventional Ginzburg-Landau contribution and the magnetization -M-fl vs. H exhibit an upturn with the field H and hysteretic effects. These findings are interpreted in terms of phase fluctuations for non-zero order parameter and attributed to inhomogeneities resulting from small amounts of Boron to Carbon substitution.