  In the normal state of high-Tc cuprates, the Hall coefficient shows
remarkable temperature dependence, and its absolute value is enhanced in
comparison with that value simply estimated on the basis of band structure. It
has been recognized that this temperature dependence of the Hall coefficient is
due to highly anisotropic quasiparticle damping rate on the Fermi surface. In
this paper we further take account of the vertex correction to the current
vertex arising from quasiparticle interactions. Then the transport current is
transformed to a large extent from the quasiparticle velocity, and is no longer
proportional to the latter. As a consequence some pieces of the Fermi surface
outside of the antiferromagnetic Brillouin zone make negative contribution to
the Hall conductivity, even if the curvature of the Fermi surface is hole-like.
The Hall coefficient is much larger at low temperatures than the estimate made
without the vertex correction. Temperature dependence of the antiferromagnetic
spin correlation length is also crucial to cause remarkable temperature
dependence of the Hall coefficient. In our treatment the Hall coefficient of
the electron-doped cuprates can be negative despite hole-like curvature of the
Fermi surface.
