Low temperature anisotropic magnetoresistance studies of the electron-doped superconductor Pr$_{1.85}$Ce$_{0.15}$CuO$_4$

We report the low temperature dc transport properties of crystals of electron-doped superconductor Pr$_{1.85}$Ce$_{0.15} $CuO$_4$(Tc~25K). By applying the magnetic field beyond H$_{C2} $, both in-plane and out-of-plane (c-axis) resistivity have a similar metallic temperature dependence with an upturn as the temperature drops below T=13K. For T<32K, a negative magnetoresistance develops in the c-axis resistivity at low magnetic field, followed by a positive magnetoresistance at high field. In contrast, the in-plane transport only shows a monotonic positive magnetoresistance in the same (H, T) region. The possible origin of these behaviors and a comparison with hole-doped superconductors will be given. (Supported by NSF DMR- 0352735)