1ST DIRECT MEASUREMENT OF THE C-AXIS RESISTIVITY IN SUPERCONDUCTING SINGLE-CRYSTALS Y1BA2CU3O7-X

We have developed a new technique to directly measure rho C and rho-ab of very small single crystals of Y1Ba2Cu3O7-x. We used this technique to measure rho C in two different crystals having different T(C)'s. In contrast with results obtained by the standard Montgomery method we find smaller values of rho-C at 300 K, although the increase of rho-C at T greater-than-or-equal-to T(C) is higher. Our data indicate the presence of localized states between the CuO2 planes due to intrinsic or extrinsic "dirty" interlayers. The c-axis resistivity follows a thermally activated law In-rho-(C) approximately (T(O)/T) with T(O) = 410 K. A correlation is observed between the lowering of T(C) and the increase of rho-C at T greater-than-or-equal-to T(C).