Upper Critical Field in the Molecular Organic Superconductor (DMET)2I3

We report the temperature dependence of the upper critical magnetic field in the quasi-onedimensional molecular organic superconductor (DMET)2I3, for magnetic field applied along the intrachain, interchain, and interplane directions. The upper critical field tends to saturation at low temperature for field in all directions and does not exceed the Pauli paramagnetic limit. Superconductivity in (DMET)2I3 thus appears to be conventional spin singlet, in contrast to the status of the isostructural Bechgaard salts. We also discuss a magnetic field-induced dimensional crossover effect in the normal metallic state which had previously appeared to be associated with superconductivity.