Hidden bulk and surface effects in the spin polarization of the nodal-line semimetal ZrSiTe

In non-magnetic materials the combination of inversion symmetry breaking (ISB) and spin-orbit coupling (SOC) determines the spin polarization of the band structure. However, a localspin polarization can also arise in centrosymmetric crystals containing ISB subunits. This isnamely the case for the nodal-line semimetal ZrSiTe where, by combining spin- and angle-resolved photoelectron spectroscopy with ab initio band structure calculations, we reveal acomplex spin polarization. In the bulk, the valence and conduction bands exhibit opposite spinorientations in two spatially separated two-dimensional ZrTe sectors within the unit cell,yielding no net polarization. We also observe spin-polarized surface states that are wellseparated in energy and momentum from the bulk bands. A layer-by-layer analysis of thespin polarization allows us to unveil the complex evolution of the signal in the bulk states nearthe surface, thus bringing the intertwined nature of surface and bulk effects to the fore