Upper critical field in electron-doped Pr$_{2-x}$Ce$_{x}$CuO$_{4-\delta }$ in parallel magnetic fields*

We report a comprehensive study of the resistive superconducting transition in the electron-doped Pr$_{2-x}$Ce$_{x}$CuO$_{4-\delta }$ films down to 1.5K for magnetic field up to 58T applied parallel to the conducting ab-planes. We find that the parallel critical field (H$_{c2//ab})$ exceeds 58T for underdoped and optimally doped films. For the overdoped films, 58T is sufficient to suppress the superconductivity. An H$_{c2//ab}$ -T phase diagram is established. A comparison between our experimental results and theories for orbital and spin pairbreaking effects will be presented.