The cooling temperatures of rectangular parallelepiped Bi1-X Sb (X) (X = 0.12 and 0.15) single-crystals with the same thickness of t = 2 mm but different width W were measured at 113 K and 290 K as a function of electric current in the magnetic field B up to 2.17 T. The magnetic field was aligned along the thickness t of a sample and the current flows along its length L through the copper leads soldered to both end surfaces of cross section (W x t), where W, t and L are parallel to the binary, bisector and trigonal axes of the single-crystal, respectively. The thermoelement was not in contact with a heat sink. The cooling temperature of Bi0.85Sb0.15 at 290 K was increased with an increase of B and was almost symmetric for the reverse of the field direction, while at 113 K it exhibited a maximum at B = +/- 0.25 T and a strong asymmetry for the field direction. The largest maximum cooling temperature Delta T (max) of Bi0.85Sb0.15 was achieved when a thermoelement has optimum dimensions so that heat energy is hardly generated at the cold side. When the single-crystal Bi0.85Sb0.15 alloy has optimum dimensions of L = 15 mm, W = 4 mm and t = 2 mm, the Delta T (max) at 290 K increased from 4.2 K in B = 0 T to 9.6 K in B = +2.17 T, so that it exceeded Delta T (max) values of 5.7 K obtained for a typical Bi2Te3 and 8.5 K measured previously for Bi single-crystal in B = +2.17 T.