Van der Waals heterostructures provide a versatile platform for tailoring electrical, magnetic, optical and spin transport properties via proximity effects. Hexagonal transition metal dichalcogenides induce valley Zeeman spin–orbit coupling in graphene, creating spin lifetime anisotropy between in-plane and out-of-plane spin orientations. However, in-plane spin lifetimes remain isotropic due to the inherent heterostructure’s three-fold symmetry. Here we demonstrate that pentagonal PdSe2, with its unique in-plane anisotropy, induces anisotropic gate-tunable spin–orbit coupling […]