Higher order terms in the geometric resonance of open orbits in unidirectional lateral superlattices

The geometric resonance of open orbits in unidirectional lateral superlattices has been examined with high magnetic-field resolution. Magnetoresistance oscillations periodic in 1/B, analogous to the well-known commensurability oscillations but orders of magnitude smaller both in magnitude and in the magnetic-field scale, have been observed superposed on the low-field positive magnetoresistance. The periodicity in 1/B can be interpreted in terms of higher order resonances.