  Silicene and germanene are key materials for the field of valleytronics.
However, interaction with the substrate, which is necessary to support the
electronically active medium, becomes a major obstacle. In the present work, we
propose a substrate (F-doped WS$_2$) that avoids detrimental effects and at the
same time induces the required valley polarization, so that no further steps
are needed for this purpose. The behavior is explained by proximity effects on
silicene/germanene, as demonstrated by first-principles calculations. Broken
inversion symmetry due to the presence of WS$_2$ opens a substantial band gap
in silicene/germanene. F doping of WS$_2$ results in spin polarization, which,
in conjunction with proximity-enhanced spin orbit coupling, creates sizable
spin-valley polarization.
