  Exploring hidden effects that have been overlooked given the nominal global
crystal symmetry but are indeed visible in solid-state materials has been a
fascinating subject of research recently. Here, we introduce a novel hidden
Zeeman-type spin polarization (HZSP) in nonmagnetic bulk crystals with
sublattice structures. In the momentum space of these crystals, the doubly
degenerate bands formed in a certain plane can exhibit a uniform spin
configuration with opposite spin orientations perpendicular to this plane,
whereas such degenerate states are spatially separated in a pair of real-space
sectors. Interestingly, we find that HZSP can manifest itself in both
centrosymmetric and non-centrosymmetric materials. We further demonstrate the
important role of nonsymmorphic twofold screw-rotational symmetry played in the
formation of HZSP. Moreover, two representative material examples, i.e.,
centrosymmetric WSe$_2$ and noncentrosymmetric BaBi$_4$O$_7$, are identified to
show HZSP via first-principles calculations. Our finding thus not only opens
new perspectives for hidden spin polarization research but also significantly
broadens the range of materials towards spintronics applications.
