The observation of acoustoelectric current saturation and domain propagation in n-type InP single crystals is reported. The electromechanical coupling constant K and the dominant acoustic frequency f are obtained from the variation of the incubation time for current decay with applied drift field. K2 = 1.0×10-3 and f = 17 GHz. The enhancement of acoustic gain in a transverse magnetic field is examined and compared to the predictions of the microscopic theory. Semiquantitative agreement can be obtained by assuming a slight scan of the dominant accoustic frequency with magnetic field. © 1971 The American Institute of Physics.