19F NMR measurements in SmFeAsO1−xFx, for 0.15≤x≤0.2, are presented. The nuclear spin-lattice relaxation rate 1/T1 increases upon cooling with a trend analogous to the one already observed in CeCu5.2Au0.8, a quasi-two-dimensional heavy-fermion intermetallic compound with an antiferromagnetic ground state. In particular, the behavior of the relaxation rate either in SmFeAsO1−xFx or in CeCu5.2Au0.8 can be described in the framework of the self-consistent renormalization theory for weakly itinerant electron systems. Remarkably, no effect of the superconducting transition on 19F 1/T1 is detected, a phenomenon which can hardly be explained within a single band model.
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