Anomalous Transport Properties in SuperconductingNd1.85Ce0.15CuO4±δ

We report a comprehensive study of the in-plane transport properties of ${\mathrm{Nd}}_{2-x}{\mathrm{Ce}}_x\mathrm{Cu}{\mathrm{O}}_{4\pm \delta }$ epitaxial thin films and crystals by both increasing and decreasing $\delta$ with Ce content fixed at $x\approx 0.15$. We find a remarkable correlation between the appearance of superconductivity and (1) a positive magnetoresistance in the normal state, (2) a positive contribution to the otherwise negative Hall coefficient, and (3) an anomalously large Nernst effect. These results strongly suggest that both holes and electrons participate in the charge transport for the superconducting phase of ${\mathrm{Nd}}_{2-x}{\mathrm{Ce}}_x\mathrm{Cu}{\mathrm{O}}_{4\pm \delta }$.