Enthalpies of formation of (X,Ni)₂YZ (X = Co, Cu, Fe, Pd) were measured by drop calorimeters.

Magnetic contribution to enthalpy of formation plays an important role.

Introducing a fourth element could stabilize an unstable Heusler structure.

Lattice parameters do not necessarily obey the Vegard's law.

It is possible to tailor properties of Heusler compounds with enough background information.