[en] The results of dc-magnetization, resistivity and ac-susceptibility studies performed on (β+γ) Ni₃₅Co₃₅Al₃₀ magnetic shape memory alloy are presented highlighting the transition between two equilibrium lattice configurations of austenite and martensite phases. The first order nature of this martensitic transition is emphasized by highlighting the presence of thermal hysteresis and phase co-existence. This transition is apparently broadened with the introduction of γ-phase in the pure β-phase Ni₃₅Co₃₅Al₃₀ alloy giving rise to a relatively large thermal hysteresis