Frustrated magnetic cycloidal structure and emergent Potts nematicity in CaMn2P2

We report neutron-diffraction results on single-crystal CaMn2P2 containing corrugated Mn honeycomb layers, and we determine its ground-state magnetic structure. The diffraction patterns consist of prominent (1/6,1/6,L) reciprocal-lattice unit (r.l.u.; L = integer) magnetic Bragg reflections, whose temperature-dependent intensities are consistent with a first-order antiferromagnetic phase transition at the Neel temperature TN = 70(1) K. Our analysis of the diffraction patterns reveals an in-plane 6 x 6 magnetic unit cell with ordered spins that in the principal-axis directions rotate by 60 degrees steps between nearest neighbors on each sublattice that forms the honeycomb structure, consistent with the PAc magnetic space group. We find that a few other magnetic subgroup symmetries (PA2/c, PC2/m, PS1 over line , PC2, PCm, PS1) of the paramagnetic P3 over line m11' crystal symmetry are consistent with the observed diffraction pattern. We relate our findings to frustrated J1 -J2 -J3 Heisenberg honeycomb antiferromagnets with single-ion anisotropy and the emergence of Potts nematicity.