Quantum Hall effect and anomalous transport in (TMTSF)(2)PF6

Under low temperatures and high magnetic fields, quasi-one dimensional orga nic conductor (TMTSF)(2)PF6 exhibits a series of transitions to field-induc ed spin density wave (FISDW). Slightly above the onset of superconductivity in (TMTSF)(2)PF6, we observe a series of intervening phases that interrupt the sequence of FISDW that gives rise to the quantum Hall effect. These ph ases can be identified either as negative quantum numbered FISDW states or a puzzling arboresecent phase. Detailed study of the QHE in (TMTSF)(2)PF6 r eveals that the transport in the FISDW phases is dominated by anomalous lon gitudinal resistivities p(xx) and p(yy) that remain finite at low temperatu res. While the quantization of sigma(xy) is not adversely affected at high magnetic fields, the transport in the intermediate magnetic field remains c omplicated. In addition, the conductivity along applied magnetic field, sig ma(zz), cannot be easily understood in terms of three-dimensional QHE and i s suggestive of the importance of inter-layer coupling.