We have shown that AuNi layers evolved towards a modulated structure along the <001> direction, consisting in one Ni-rich plane and (n–1) Au-rich planes. This ordered phase is stable in a narrow temperature range and the period n is slightly dependant on the x_Ni composition. XRD diagrams simulation, structure calculation and TEM observations carried out with x_Ni = 0.4 allow us to propose that the ordering process begins on very small domains of various ordered structure and that the domains with the most stable structure then grow up to the others cost. Our model for the stable phase is not the most perfect one but a partially ordered structure with a relaxation in the Au-planes/Ni-plane distance of about 5 %.