A Bi.sub.1-xSb.sub.x thin film is provided that includes a Dirac-cone with different degrees of anisotropy in their electronic band structure by controlling the stoichiometry, film thickness, and growth orientation of the thin film, so as to result in a consistent inverse-effective mass tensor including non-parabolic or linear dispersion relations.
 This invention was made with government support under Grant Nos. DE-SC0001299 and DE-FG02-09ER46577 awarded by the Department of Energy and under Contract No. FA9550-10-1-0533 awarded by the U.S. Air Force. The government has certain rights in the invention.