Organic conductors of tau-phase

Cation radical salts based on ethylenedioxy-S,S-dimethylethylenedithio-tetr athiafulvalene, pyrazino-S,S-dimethylethylenedithio-tetrathiafulvalene and ethylenedioxy-venylenedithio-tetrathiafulvalene with linear counter anions are crystallized in the tau-phase. They exhibit logarithmic temperature dep endence of the resistivity and negative magnetoresistance at low temperatur es and low magnetic fields, while their magnetoresistance shows maxima (and minima) at higher magnetic fields and lower temperatures.