SUPERCONDUCTIVE PROPERTIES OF A YBA2CU3O7-DELTA SINGLE-CRYSTAL PREPARED BY CRYSTAL PULLING

We present anisotropic transport properties for a YBa2Cu3O7-delta sing le crystal prepared by the pulling method. The resistivity in the ab-p lane (rho(ab)), for both the as-grown sample and the oxygen-annealed s ample, shows good metallic behavior. The resistivity just above T(c) i s approximately 2 x 10(-5) OMEGA cm. On the other hand, the resistivit y along the c-axis (rho(c)) changes from semiconductor-like behavior f or the as-grown sample to metallic behavior for the oxygen-annealed sa mple. In addition, any trace of Josephson characteristics is not obser ved for our samples. The metallic behavior of rho(c) suggests that the Cu-0 chain changes its conduction with hole doping, in addition to it s role as a carrier source for the CuO2 planes.