Figure S1 to Figure S21

See the supplementary materials for the relevant parameters of the SVSiN$_{2}$ bilayer with different stacking configurations and magnetic orders; the crystal structure, band structure, valley splitting of the SVSiN$_{2}$ monolayer; phonon spectra of the SVSiN$_{2}$ bilayers with different stackings and magnetic orders; spin-projected band structure of various stacked SVSiN$_{2}$ bilayers with different magnetic orders; Berry curvature and circular polarization of various stacked SVSiN$_{2}$ bilayer with different magnetic orders; schematic diagram of atomic/spin-projected band structure and the band gap variations of various stacked SVSiN$_{2}$ bilayers with different magnetic orders under electric fields; the conduction/valence band spin splitting and valley splitting of various stacked SVSiN$_{2}$ bilayers with different magnetic orders influenced by electric fields. The planar-averaged electrostatic potential, planar-averaged charge density, and three-dimensional charge density difference; the ferroelectric switching pathway and energy barrier of the SVSiN$_{2}$ bilayer; the spin-projected band structures of the AA stacked bilayer with AFM order and the AC stacked bilayer with FM order.