Magnetotransport has been investigated in high-purity bismuth crystals in s
tatic magnetic fields as high as 20 T and temperatures as low as 25 mK. Thi
s high B/T ratio permits observation of pronounced Shubnikov-de Haas oscill
ations over a wide field range and up to fields where most of the carriers
are in the lowest Landau level. For transport currents in the bisectrix or
binary directions, and field in the perpendicular trigonal direction, we ha
ve observed doublet splittings centered on each Shubnikov-de Haas oscillati
on. These splittings exhibit a quadratic dependence on field and disappear
before the last oscillation. Our observations allow us to conclude unambigu
ously that when the Landau-level index is as high as 2, the carriers are fu
lly polarized and the g factor for holes with the field in the trigonal dir
ection is 35.3(4).