Resonance of the photo-emf induced by far-IR light in the presence of a mag
netic field oriented parallel to the plane of the well is observed in a GaS
b-InAs-GaSb semimetal quantum well. It is inferred that the effect is due t
o optical transitions between sublevels of the first size-quantization leve
l. (C) 1998 American Institute of Physics. [S0021-3640(98)01022-6].