SUPERCONDUCTIVITY AND MAGNETIC-FIELD-INDUCED SPIN-DENSITY WAVES IN THE (TMTTF)(2)X FAMILY

We report magnetotransport measurements in the quasi one dimensional ( Q-1-D) organic conductor (TMTTF)(2)Br at pressures up to 26 kbar. down to 0.45 K in magnetic fields up to 19 T along the c direction. It is found that a superconducting ground state is stabilized under 26 kbar at T-c = 0.8 K. No magnetic field induced spin density wave (FISDW) t ransitions are observed below 19T unlike other Q-1-D superconductors p ertaining to the selenium series. The computed amplitude of the interc hain coupling along transverse directions is unable to explain the mis sing FISDW instability.