  We show that a sharp dependence of the Hall coefficient $R$ on the magnetic
field $B$ arises in two-dimensional electron systems with randomly located
strong scatterers. The phenomenon is due to classical memory effects. We
calculate analytically the dependence $R(B)$ for the case of scattering by hard
disks of radius $a$, randomly distributed with concentration $n_0\ll1/a^2$. We
demonstrate that in very weak magnetic fields ($\omega_c\tau \lesssim n_0a^2$)
memory effects lead to a considerable renormalization of the Boltzmann value of
the Hall coefficient: $\delta R / R \sim 1 .$ With increasing magnetic field,
the relative correction to $R$ decreases, then changes sign, and saturates at
the value $\delta R / R \sim -n_0a^2 .$ We also discuss the effect of the
smooth disorder on the dependence of $R$ on $B$.
