  We study the magnetic susceptibility of a layered semiconductor BiTeI with
giant Rashba spin splitting both theoretically and experimentally to explore
its orbital magnetism. Apart from the core contributions, a large
temperature-dependent diamagnetic susceptibility is observed when the Fermi
energy E_F is near the crossing point of the conduction bands, while the
susceptibility turns to be paramagnetic when E_F is away from it. These
features are consistent with first-principles calculations, which also predict
an enhanced orbital magnetic susceptibility with both positive and negative
signs as a function of E_F due to band (anti)crossings. Based on these
observations, we propose two mechanisms for an enhanced paramagnetic orbital
susceptibility.
