Experimental results involving the substitution of U atoms by Gd and D
y in the spin fluctuation system UAl2 are studied in terms of the theo
ry proposed by Doniach and Wohlfarth. Besides the intraband f-f Coulom
b interaction, the model contains the Zener coupling between localized
4f spins and itinerant 5f states. The induced effective f-f interacti
on increases the proximity to a magnetic instability.