EVIDENCE OF CHARGE-CARRIER INTERACTION ABOVE T-C IN THE ND1.85CE0.15CUO4+DELTA SUPERCONDUCTOR

Resistivity, thermopower, and magnetic susceptibility of the Nd1.85Ce0 .15CuO4+delta n-type superconductor have been measured on samples with well-known charge carrier density. Superconductivity is achieved only for charge carrier densities greater than a threshold value. When thi s value is approached, mobility drops to less than a tenth of the valu e for nonsuperconducting samples, the effective mass increases from 8m (e) to 25m(e), and susceptibility falls to lower values. All these phe nomena are apparent well above T-c, thus indicating a charge carrier i nteraction above T-c. [S0163-1829(98)01438-6].