  We study normal state electrical, thermoelectrical and thermal transport in
polycrystalline BiS2-based compounds, which become superconducting by F doping
on the O site. In particular we explore undoped LaOBiS2 and doped
LaO0.5F0.5BiS2 samples, prepared either with or without high pressure
annealing, in order to evidence the roles of doping and preparation conditions.
The high pressure annealed sample exhibits room temperature values of
resistivity ro around 5 mohmcm, Seebeck coefficient S around -20 microV/K and
thermal conductivity k around 1.5 W/Km, while the Hall resistance RH is
negative at all temperatures and its value is -10-8 m3/C at low temperature.
The sample prepared at ambient pressure exhibits RH positive in sign and five
times larger in magnitude, and S negative in sign and slightly smaller in
magnitude. These results reveal a complex multiband evolution brought about by
high pressure annealing. In particular, the sign inversion and magnitude
suppression of RH, indicating increased electron-type carrier density in the
high pressure sample, may be closely related to previous findings about change
in lattice parameters and enhancement of superconducting Tc by high pressure
annealing. As for the undoped sample, it exhibits the 10 times larger
resistivity, 10 times larger |S| and 10 times larger |RH| than its doped
counterpart, consistently with its insulating nature. Our results point out the
dramatic effect of preparation conditions in affecting charge carrier density
as well as structural, band and electronic parameters in these systems.
