is a transition-metal nitride with Mn and Si ions displaying an ordered distribution on the cation sites of a distorted wurtzite-derived structure. The ions reside on a three-dimensional (3D) diamondlike covalent network with strong superexchange pathways. We simulate its electronic structure and find that the N anions in act as - and -donors, which serve to enhance the N-mediated superexchange, leading to the high Néel ordering temperature of = 443 K. Polycrystalline samples of were prepared to reexamine the magnetic structure and resolve previously reported discrepancies. An additional magnetic canting transition is observed at = 433 K and the precise canted ground-state magnetic structure has been resolved using a combination of density functional theory (DFT) calculations and powder neutron diffraction. The calculations favor a -type antiferromagnetic spin order with lowering to . Irreducible representation analysis of the magnetic Bragg peaks supports the lowering of the magnetic symmetry. The computed model includes a rotation of the magnetic spins away from the crystallographic axis consistent with measured powder neutron diffraction data modeling and a small canting of .