H12 anchor: D019-type (Ni3Sn prototype) Mn3Bi, P6_3/mmc #194, 8 atoms (Mn 6h x=0.83865, Bi 2c). Built for the permanent-magnets program H12 Mn-Bi hypothesis; lattice bond-matched to LTP MnBi (Mn-Bi 2.912 A). Validated: SG 194 at symprec 0.01 and 0.1, ordered, dmin Mn-Mn 2.827 A, rho 9.000 g/cm3.