RESISTIVITY, HALL-EFFECT, NERNST EFFECT AND THERMOPOWER IN THE MIXED STATE OF BI-BASED AND TL-BASED HIGH-TC SUPERCONDUCTORS

We present measurements of the electric resistivity, the Hall effect, the Nernst effect and the thermopower in the mixed state of Bi1.76Pb0.24Sr2Ca2Cu3Odelta and of Tl2Ba2Ca2Cu3Odelta We find a large broadening of the resistive transition independent of the current direction with respect to the magnetic field, thermally activated behavior of the resistivity rho at low temperatures and a strongly non-linear dependence of rho on the magnetic field. The Hall coefficient R(H) is strongly temperature-dependent and shows a pronounced sign change in small magnetic fields. We find a large Nernst effect, from which the entropy/heat transported by the vortices is estimated. The thermopower is larger by a factor of 1000 compared to what is expected from the conventional theory of flux motion. It is remarkably similar to the resistivity.