Cyclotron resonance of Kane electrons observed in Cd3As2

We report on infrared transmission and reflectivity experiments performed on Cd
₃
As
₂
in a wide range of the photon energies and magnetic fields. The observed magneto-optical response unambiguously indicates the presence of 3D massless charge carriers. The detailed analysis of cyclotron resonances implies the presence of massless Kane electrons at a large energy scale, while the symmetry-protected 3D Dirac cones may appear at a small scale.