[en] Low temperature (T>0.6K) Electron Spin Resonance (ESR) experiments were carried out for the heavy-fermion compounds UBe₁₃ and UPt₃ doped with several Rare Earth ions. The measured Korringa rate for all rare earth were always within the same order of magnitude of a normal metal and no significant deviation from the linear behavior was observed. The experimental results lead to the conclusion that the coupling between the uranium ion and the rare earth ion through the s-f electron interaction is very small, if any. (author)