We have observed a sharp drop by several percent in the conductance of a GaAs/${\mathrm{Ga}}_{0.77}$${\mathrm{Al}}_{0.23}$As heterojunction with decreasing temperature near 4 K. The width of the transition is approximately 0.5 K. The transition has a strong magnetic field dependence which is both anisotropic and hysteretic. Below the transition the dc conductivity is strongly non-Ohmic. We attribute this striking behavior to the formation of a mixed density wave, involving both charge- and spin-density-wave characteristics.

• Received 19 November 1985

DOI:https://doi.org/10.1103/PhysRevB.33.2916