A new monoclinic structure type for ternary gallide MgCoGa2

The crystal structure of MgCoGa₂ (magnesium cobalt digallide) was solved by direct methods and refined in two space groups as P2₁/c (standard choice) and P2₁/n (non‐standard choice). The refined lattice parameters for the standard choice are a = 5.1505 (2), b = 7.2571 (2), c = 8.0264 (3) Å and β = 125.571 (3)°, and for the non‐standard choice are a = 5.1505 (2), b = 7.2571 (2), c = 6.5464 (2) Å and β = 94.217 (3)°. All parameters for MgCoGa₂ refined to R₁ = 0.027 and wR₂ = 0.042 using 594 reflections. The crystal structure peculiarities of this compound are discussed. Particular attention has been given to relationships with other similar structures, such as YPd₂Si and Fe₃C. Crystallographic analysis, together with linear muffin‐tin orbital electronic structure calculations, reveals the presence of three‐dimensional polyatomic nets with partial covalent bonding between the Ga atoms.