ANISOTROPIC NORMAL-STATE MAGNETOTHERMOPOWER OF SUPERCONDUCTING ND1.85CE0.15CUO4 CRYSTALS

We report measurements of the normal-state in-plane thermopower S of superconducting Nd1.85Ce0.15CuO4 crystals in magnetic fields (B) up to 9 tesla. When the magnetic field is parallel to the CuO2 planes, we find that S is B independent indicating the absence of spin entropy effects. As B is oriented perpendicular to the CuO2 planes, a giant negative magnetothermopower is found suggesting an orbital effect which cannot be understood within existing models. The normal-state thermopower tends to vanish as T goes to zero when superconductivity is destroyed by a large magnetic field, consistent with thermal transport in conventional metals.