  Here we theoretically investigate the valley-dependent transmission of
particles through a combined electric and magnetic barrier in the $\alpha-T_3$
model which interpolates between the honeycomb and the dice lattices. We put
forward that the combination of the Fabry-P\'erot interferences and the
magnetic field leads to a perfect transmission for one valley and a suppression
of the transmission for the other valley. When only one of the barriers
(magnetic or electric) is present, no valley polarized current can be produced.
By tuning the Fermi energy, this valley-dependent peculiar behavior can be used
as valley filtering. Our results show that highly efficient valley filtering
with maximum conductivity and polarization can be achieved by controlling the
value of the magnetic field and the electric barrier width and height.
