Magnetoreflection in Bismuth

Direct interband transitions have been observed in the infrared magnetoreflection of single-crystal bismuth at low temperatures. They are manifested by oscillations which are almost periodic in $\frac{1}{H}$. Analysis in terms of a two-band model yields the energy gap, ${\epsilon }_g=0.015\mathrm{}\pm 0.002$ eV, and also the cyclotron masses at the bottom of the conduction band for two orientations of the magnetic field with respect to the crystallographic axes. Within the resolution of the instrument, the $g$ factors of the conduction and valence bands are equal.