  Measurements of commensurability oscillations in GaAs/AlGaAs two-dimensional
(2D) hole systems grown on GaAs (311)A substrates reveal a remarkable
anisotropy: the amplitude of the measured commensurability oscillations along
the [$\bar{2}$33] direction is about 100 times larger than along [01$\bar{1}$].
For 2D electron systems at similar interfaces, however, we observe nearly
isotropic oscillations, suggesting that the anomalous anisotropy is intrinsic
to GaAs 2D holes at the (311)A interface.
