On Ambient-Pressure Superconductivity in Organic Conductors: Electrical Properties of (DMET)2I3, (DMET)2I2Br and (DMET)2IBr2

We discovered superconductivity at ambient pressure in (DMET) 2 I 3 at 0.47 K and in (DMET) 2 IBr 2 at 0.59 K (midpoints), where DMET is (dimethyl(ethylenedithio)diselenadithiafulvalene), while in (DMET) 2 I 2 Br, superconductivity was not observed down to 0.5 K. In the DMET salts, those with smaller molar volume exhibit higher transition temperature, contrary to the BEDT-TTF salts. The effect of the disorder of the anion orientation on superconductivity is discussed.