Unconventional Field Dependent Magnetoresistance in Q1D Conductors

We report on magnetoresistance measurements in the organic metal (TMTSF)$_2$ClO$_4$ at specific crystal orientations in a magnetic field. In the regime of interference-commensurate ``L-N-type" oscillations, field sweeps at resistance minima and maxima (vs. angle) show qualitatively different magnetoresistance behavior. At minima, $R(B)$ tends to saturation at large $B$ (to 10T at 0.1K). At maxima, $R$ follows an empirical formula containing only linear and quadratic terms, with the former coefficient decreasing and the latter increasing as the field is tilted away from the highly conducting axis. We interpret these two regimes of behavior (maxima and minima) in terms of dimensional crossovers based on Lebed's recent theory.