Study on the thermopower of Bi intercalated TiS2: Evidence of thin, lens-shaped Fermi pockets

The temperature dependent thermopower of BixTiS2 (x=0x=0, 0.05, 0.15, 0.25) was investigated in the temperature range from 7 to 300 K. The thermopower of all samples show a metallic behavior with diffusion thermopower dominating at high temperatures and a peak of phonon-drag contribution at low temperatures. They could be scaled to S=S∗×S(T/T∗)S=S∗×S(T/T∗), indicating that the Bi intercalation does not change the scattering mechanism. The thermopower should be attributed to the special lens-shaped Fermi pockets. With increasing Bi intercalation, the Fermi pockets expand, and each Bi atom transfers five electrons to the host layers.