Thermodynamic properties of the organic superconductor κL-(ET)2Ag(CF3)4&middotTCE

We present specific-heat, magnetization, and ac-susceptibility measurements of the recently discovered organic superconductor κL-(ET)2Ag(CF3)4&middotTCE, where ET (= BEDT-TTF) stands for bisethylenedithio-tetrathiafulvalene and TCE is the neutral solvent 1,1,2-trichloroethane. We observed a very large anisotropy of the critical field B* extracted from ac-susceptibility data in accord with the enhanced ET-layer separation due to the large anions. The strong frequency dependence of B* reveals the weak pinning forces in the material. Magnetization and specific-heat, C, measurements prove the bulk effect of superconductivity. The linear coefficient of C is γ 50 mJ/molK2 which is a factor 9 larger than expected from a free-electron picture. Indications for strong coupling are found.