The class of Dirac-type materials has been recently expanded to include systems hosting massless charge carriers within their 3D conical band structures. Using high-field magneto-transmission experiments, we have identified one of the very first such materials – HgCdTe, tuned to the point of the topological semiconductor-to-semimetal transition. The presence of a single 3D conical band located in the center of the Brilouin zone is shown by, e.g., specific absorption coefficient that increases linearly with the photon energy and by characteristic magneto-optical response with a well-defined √B dependence, see figures below.
