C-Type Antiferromagnetic Structure of Topological Semimetal CaMnSb₂

Determination of the magnetic structure and confirmation of the presence or absence of inversion ( <?CDATA P?> P ) and time reversal ( <?CDATA T?> T ) symmetry is imperative for correctly understanding the topological magnetic materials. Here high-quality single crystals of the layered manganese pnictide CaMnSb 2 are synthesized using the self-flux method. De Haas–van Alphen oscillations indicate a nontrivial Berry phase of ∼ π and a notably small cyclotron effective mass, supporting the Dirac semimetal nature of CaMnSb 2 . Neutron diffraction measurements identify a C-type antiferromagnetic structure below T N = 303(1) K with the Mn moments aligned along the a axis, which is well supported by the density functional theory (DFT) calculations. The corresponding magnetic space group is Pn ′ m ′ a ′, preserving a <?CDATA P?> P × T symmetry. Adopting the experimentally determined magnetic structure, band crossings near the Y point in momentum space and linear dispersions of the Sb 5p y , z bands are revealed by the DFT calculations. Furthermore, our study predicts the possible existence of an intrinsic second-order nonlinear Hall effect in CaMnSb 2 , offering a promising platform to study the impact of topological properties on nonlinear electrical transports in antiferromagnets.