[en] The effect of atomic order on the martensitic phase transition and magnetic properties of stoichiometric Ni₂MnGa has been investigated in a sample quenched from 1000 deg C. Magnetization, resistivity and x-ray diffraction measurements indicate that the structural phase transition occurs at ∼ 103 K, substantially lower than the value reported for samples quenched from 800 deg C and ordered in the Heusler L2₁ structure. A small reduction in the ferromagnetic moment was also observed, although the Curie temperature remained largely unaffected. The electronic Sommerfeld coefficient obtained from heat capacity measurements is enhanced but smaller than that observed for the 800 deg C quenched sample. The results are consistent with band structure calculations and the electronic changes brought about by atomic disorder