Phenomenology and sign change of the Hall resistivity near the superconducting transition of polycrystalline DyBa2Cu3O7-delta

Measurements of the temperature dependence of the electrical resistivity an d the Hall effect in the normal and superconducting states of a ceramic DyB a2Cu3O7-delta superconductor are reported. In high temperatures the diagona l resistivity is proportional to T, whereas the Hall response exhibits a 1/ T dependence and the cotangent of the Hall angle is proportional to T-2. Up on decreasing the temperature, the Hall response shows a sign reversal clos e to T-c, goes through a negative maximum and vanishes close to the so-call ed zero-resistance temperature. The aim of this report is to show that the sign change occurs in the temperature region dominated by thermal fluctuati ons in the order parameter.