Figure 1: Crystal structures and phase diagram of $\text{Ni-Mn-Sn}$. The shadowed area in the phase diagram is the region where $\text{Ni-Mn-Sn}$, on cooling, first becomes ferromagnetic and later transforms martensitically. (A) The $L{2}_1$ structure showing also the relationship with the tetragonal unit cell. (B) Tetragonal ($L{1}_0$) unit cell. (C) The tetragonal unit cell viewed from top. (D) The martensitic structure constructed from nanotwinned variants of the $L{1}_0$ structure.