  The resistivity $\rho$ and Hall resistivity $\rho_H$ are measured on FeSe at
pressures up to $P$ = 28.3 kbar in magnetic fields up to $B$ = 14.5 T. The
$\rho(B)$ and $\rho_H(B)$ curves are analyzed with multicarrier models to
estimate the carrier density and mobility as a function of $P$ and temperature
($ T\leqslant$ 110 K). It is shown that the pressure-induced antiferromagnetic
transition is accompanied by an abrupt reduction of the carrier density and
scattering. This indicates that the electronic structure is reconstructed
significantly by the antiferromagnetic order.
