INFLUENCE OF THERMAL AND STRUCTURAL FLUCTUATIONS ON ANISOTROPIC RESISTIVITY AND NONLINEAR TRANSPORT-PROPERTIES OF REBA2CU3O7-DELTA (RE=Y,TM) SINGLE-CRYSTALS

The rho(ab) and rho(c) resistivity components of ReBa2Cu3O7-delta (Re= Y, Tm) single crystals have been studied both above and below T(C). Al l samples have close rho(ab)(T) values in normal state and differ main ly by the transition width. We have found that the superconducting tra nsition region isn't described by the thermal fluctuations only and is influenced by structural fluctuations too. For the best sample the an isotropy of the resistivity is approximately 40 and shows weak tempera ture dependence. This behavior is shown to be ''intrinsic'' property o f ReBa2Cu3O7-delta system. For the less perfect samples the resistivit y anisotropy is found to be highly temperature dependent which is conn ected with the layered structural fluctuations. Below T(C) the I-V cur ves show powerlike E approximately j(n) behaviour with sharp n increas e between 1 and 3.