A NEW 9-K SUPERCONDUCTING ORGANIC SALT COMPOSED OF THE BIS(ETHYLENEDITHIO) TETRATHIAFULVALENE (ET) ELECTRON-DONOR MOLECULE AND THE TETRAKIS (TRIFLUOROMETHYL) CUPRATE (III) ANION, [CU(CF3)4]-

We report the discovery of a second, higher-T(c) superconducting organic charge-transfer salt derived from the electron-donor molecule BEDT-TTF (or ET), the novel organometallic anion [Cu(CF3)4]-, and the neutral solvent molecule 1,1,2-trichloroethane (TCE). We have very recently reported that this charge-transfer system yields a new superconducting k phase salt, k(L)-(ET)2Cu(CF3)4.TCE, with inductive onset T(c) = 4.0 K at ambient pressure. This k phase salt (k denotes a particular packing arrangement of the ET organic donor molecules) is electrocrystallized in the habit of hexagonal plates. Crystals possessing a needle-like habit electrocrystallize simultaneously with these plates, and we find these needles to be a distinctly different superconducting phase with diamagnetic onset T(c) = 9.2 +/- 0.1 K at ambient pressure. On the basis of our experiments, we denote this new superconducting phase as k(H)-(ET)2Cu(CF3)4.(TCE)(x),X<1