PACS. 74.70.Kn -Organic superconductors. PACS. 74.62.Dh -Effects of crystal defects, doping and substitution.Abstract. -The study of the anion ordered (T M T SF )2ClO 4(1−x) ReO4x solid solution in the limit of a low ReO − 4 substitution level (0 ≤ x ≤ 17%) has revealed a new and interesting phase diagram. Superconductivity is drastically suppressed as the effect of ReO − 4 non magnetic point defects increases following the digamma behaviour for usual superconductors in the presence of paramagnetic impurities. Then, no long range order can be stabilized above 0.1K in a narrow window of substitution. Finally, an insulating SDW ground state in ReO − 4 -rich samples is rapidly stabilized with the decrease of the potential strength leading to the doubling of the transverse periodicity. This extensive study has shown that the superconducting order parameter must change its sign over the Fermi surface.c EDP Sciences

We present a study of the superconducting properties (Tc and Hc2) in the solid solution (T M T SF )2(ClO4) (1−x) (ReO4)x with a ReO − 4 nominal concentration up to x = 6%. The dramatic suppression of Tc when the residual resistivity is increased upon alloying with no modification of the Fermi surface is the signature of non-conventional superconductivity . This behaviour strongly supports p or d wave pairing in quasi one dimensional organic superconductors. The determination of the electron lifetime in the normal state at low temperature confirms that a single particle Drude model is unable to explain the temperature dependence of the conductivity and that a very narrow zero frequency mode must be taken into account for the interpretation of the transport properties.