Anisotropic superconductivity in epitaxial MgB2 films

We measure the in-plane electrical resistivity of epitaxial MgB2 thin films in magnetic fields to 60 T and estimate the superconducting upper critical field H-p(c) (0) 24 +/-3 T for field oriented along the c-axis, and H-g(ab )(0)approximate to 30 +/-2 T in the plane of the film. We find the zero-tem perature coherence lengths xi (c)(0)approximate to 30 Angstrom and xi (ab)( 0)approximate to 37 Angstrom to be shorter than the calculated electronic m ean free path l approximate to 100 +/- 50 Angstrom, which places our films in the clean limit. These large upper critical fields make MgB2 a strong ca ndidate for technological applications. (C) 2001 Published by Elsevier Scie nce B.V.