  The sign change in the Hall conductivity has been studied in thin amorphous
Nb$_{1-x}$Ge$_x (x\approx$0.3) films. By changing the film thickness it is
shown that the field at which the sign reversal occurs shifts to lower values
(from above to below the mean-field transition field $H_{c2}$) with increasing
film thickness. This effect can be understood in terms of a competition between
a positive normal and a negative fluctuation contribution to the Hall
conductivity.
