COMMENSURATE FINE-STRUCTURE IN ANGULAR-DEPENDENT STUDIES OF (TMTSF)2CLO4

Clear fine-structure oscillations in magnetoresistance and torque magnetization are observed at low temperatures in the organic superconductor (TMTSF)2ClO4 as a function of sample orientation in a magnetic field. These fine structures appear as resistance minima and torque maxima at specific field orientations, with one-to-one correspondence. The angular positions of the features are independent of magnetic field, temperature, and cooling rate (disorder), while their magnitudes depend strongly on all three. We compare these observations with a recent prediction by Lebed' and Bak of resistance, but not magnetization, anomalies expected to arise at special "magic angles" in field.