  Although SbSe2-based layered compounds have been predicted to be
high-performance thermoelectric materials and topological materials, most of
these compounds obtained experimentally have been insulators so far. Here, we
present the effect of Bi substitution on the thermoelectric properties of
SbSe2-based layered compounds NdO0.8F0.2Sb1-xBixSe2 (x = 0-0.4). The room
temperature electrical resistivity is decreased to 8.0 * 10^-5 ohmm for x =
0.4. The electrical power factor is calculated to be 1.4 * 10^-4 W/mK^2 at 660
K, which is in reasonable agreement with combined Jonker and Ioffe analysis.
The room-temperature lattice thermal conductivity of less than 1 W/mK is almost
independent of x, in contrast to the point-defect scattering model for
conventional alloys. The present work provides an avenue for exploring
SbSe2-based insulating and BiSe2-based conducting systems.
