It was recently noted that in certain nonmagnetic centrosymmetric compounds,spin-orbit interactions couple each local sector that lacks inversion symmetry,leading to visible spin polarization effects in the real space,dubbed “hidden spin polarization (HSP)”.However,observable spin polarization of a given local sector suffers interference from its inversion partner,impeding material realization and potential applications of HSP.Starting from a single-orbital tight-binding model,we propose a nontrivial way to obtain strong sector-projected spin texture through the vanishing hybridization between inversion partners protected by nonsymmorphic symmetry.The HSP effect is generally compensated by inversion partners near the Γ point but immune from the hopping effect around the boundary of the Brillouin zone.We further summarize 17 layer groups that support such symmetry-assisted HSP and identify hundreds of quasi-2D materials from the existing databases by first-principle calculations,among which a group of rare-earth compounds LnIO (Ln =Pr,Nd,Ho,Tm,and Lu) serves as great candidates showing strong Rashba-and Dresselhaus-type HSP.Our findings expand the material pool for potential spintronic applications and shed light on controlling HSP properties for emergent quantum phenomena.