  The semiclassical transport theory is especially powerful for investigating
galvanomagnetic effects. Generally, the semiclassical theory is applicable only
in weak fields because it does not consider Landau quantization. Herein, we
extend the conventional semiclassical theory by considering Landau quantization
through the field dependence of carrier density in semimetals. The extended
semiclassical theory is applicable even in strong fields, where Landau
quantization is noticeable. Using this new approach, we explain the qualitative
change in the angular dependence of transverse magnetoresistance (TMR),
anisotropic magnetoresistance (AMR), and planar Hall effect (PHE) in bismuth
with an increase in the magnetic field. This unveils the puzzle of nontrivial
field-induced changes in TMR, AMR, and PHE observed recently in semimetal
bismuth.
