N-type Bi100-xSbx alloys have the highest thermoelectric figure of merit (zT) of all materials below 200K; here we investigate how filling multiple valence band pockets at T and H-points of the Brillouin zone produces high zT in p-type Sn-doped material. This approach, theoretically predicted to potentially give zT>1 in Bi, was used successfully in PbTe. We report thermopower, electrical and thermal conductivity (2 to 400K) of single crystals with 12<x<37 and polycrystals (x=50-90), higher Sb concentrations than previous studies. We obtain a 60% improvement in zT to 0.13.
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