Two-dimensional spin-uncompensated momentum density distributions, $rho_{rm s}^{2D}({bf p})$s, were reconstructed in magnetite at 12K and 300K from several measured directional magnetic Compton profiles. Mechanical de-twinning was used to overcome se
vere twinning in the single crystal sample below the Verwey transition. The reconstructed $rho_{rm s}^{2D}({bf p})$ in the first Brillouin zone changes from being negative at 300 K to positive at 12 K. This result provides the first clear evidence that electrons with low momenta in the minority spin bands in magnetite are localized below the Verwey transition temperature.
