Abstract
The Hall effect has been measured on an isotropic polycrystalline
Bi sample, from 5 K up to room temperature. It appears
that the Hall voltage exhibits a strong asymmetry under sign
reversal of magnetic field. This peculiar effect becomes more
pronounced as the temperature decreases.
It is shown that this astonishing behavior, at first glance, can
be ascribed to the "Umkehr" effect, previously predicted from a
phenomenological point of view, for the off-diagonal components of
the magnetoresistivity tensor, for 
m crystallographic
point group.