Cyclotron-resonance experiments on conduction electrons in InSb are performed in crossed magnetic and electric fields with use of a metal-oxide-semiconductor structure. The data are successfully described on the basis of a three-level k·p band model. The electron behavior in crossed fields is interpreted as a spectacular example of an analogy between electrons in narrow-gap semiconductors and relativistic electrons in vacuum.

• Received 20 March 1985

DOI:https://doi.org/10.1103/PhysRevLett.55.983