Anisotropy of the upper critical field of the organic superconductor lambda-(BETS)(2)GaCl4

The upper critical field Ba of the organic superconductor lambda-(BETS)(2)G aCl4 has been determined from resistance measurements for orientation of th e magnetic field along three perpendicular crystallographic directions. The Ginzburg-Landau coherence length was estimated from the slope of B-c2(T) c urve near T-c as 12.5 nm, 1.6 nm, and 12.5 nm for the a*-, b*-, and c-direc tions. Angular dependence of the critical field within highly conducting ac plane at 1.5 K was shown to possess two-fold symmetry, which can be relate d to the band structure anisotropy.