Upper critical field of the spin ladder system Sr2.5Ca11.5Cu24O41

Abstract We present transport measurements under pressure of the upper critical field of the superconducting spin ladder system Sr 2.5 Ca 11.5 Cu 24 O 41 . The temperature dependence and anisotropy of H c2 at low field is compared to results in high- T c superconductors and in 1D organic superconductors, as well as to simple theoretical predictions.