RESISTIVITY ANOMALIES ABOVE THE SUPERCONDUCTING TRANSITION IN Y1BA2CU3O7-DELTA CRYSTALS AND NONUNIFORMLY DISTRIBUTED CRITICAL-TEMPERATURE INHOMOGENEITIES

We report the observation of a sharp peak (20% of the normal resistivi ty), just above the superconducting transition, in the curve of the ab plane electrical resistivity versus temperature, rho(ab)(T), of some non-fully oxygenated Y1Ba2Cu3O7-delta crystals, with transition temper atures, T(c), below 90 K. The peak amplitude decreases in the presence of an applied magnetic field perpendicular to the ab plane and it is also affected by the electrical-contact configuration or by further re -oxygenation of the crystals. This resistivity anomaly may easily be e xplained by assuming the presence of T, inhomogeneities associated wit h small stoichiometric (oxygen-content) inhomogeneities, at long lengt h scales, non-uniformly distributed in the crystals. Also, we show tha t depending on their spatial distribution, the T(c) inhomogeneities ma y just deform (but without a peak) the resistivity versus temperature curve above T(c), very close to the transition, without appreciably br oadening the measured resistive transition. These results may help to the understanding of the anomalies observed near T(c) in different tra nsport properties and materials by other authors.