  Multiple anomalous features in electronic spectra of metals with kagome
lattice structure -- van Hove singularities, Dirac points, and flat bands --
imply that materials containing this structural motif may lie at a nexus of
topological and correlated electron physics. Due to the prospects of such
exceptional electronic behavior, the recent discovery of superconductivity
coexisting with charge-density wave (CDW) order in the layered kagome metals
AV$_{3}$Sb$_{5}$ (A=K,Rb,Cs) has attracted considerable attention. Notably,
these kagome metals express unconventional magnetotransport behavior, including
a linear-in-H diagonal resistivity at low fields, and an even more peculiar,
nonmonotonic sign-changing behavior of the Hall resistivity, which has been
speculated to arise from a chiral CDW. We argue here that this unusual
magnetotransport derives not from such unconventional phenomena, but rather
from the unique fermiology of the AV$_{3}$Sb$_{5}$ materials. Specifically, it
is caused by a large, concave hexagonal Fermi surface sheet formed in the close
proximity to the van Hove singularities, which is backfolded into a small
hexagonal sheet and two large triangular sheets in the CDW state. We introduce
a model of the electronic structure of these Fermi surface sheets that allows
for a full analytical treatment within Boltzmann kinetic theory and that
enables semi-quantitative fits of our transport data. Specifically, we find
that the anomalous magnetotransport behavior is caused by the confluence of
strong reduction of the Fermi velocity near the van Hove singularities located
near the vertices of the hexagonal sheet and sharp corners in Fermi surface
generated by the CDW reconstruction.
