We report on Landau-level spectroscopy of an epitaxially grown thin film of the topological insulator Sb2Te3,
complemented by ellipsometry and magnetotransport measurements. The observed response suggests that
Sb2Te3 is a direct-gap semiconductor with the fundamental band gap located at the point or along the trigonal
axis, and its width reaches Eg = (190 ± 10) meV at low temperatures. Our data also indicate the presence of
other low-energy extrema with a higher multiplicity in both the conduction and valence bands. The conclusions
based on our experimental data are confronted with and to a great extent corroborated by the electronic band
structure calculated using the GW method
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