[en] The large variation of the hyperfine fields (HFF) at Co nuclei in several series of rare earth-cobalt intermetallic compounds is interesting since it may be related partly to large anisotropy energies of these materials. In RCo₂ the Co atoms occupy the 3m sites with the three fold axis lying along one of the <111> directions. The Co sites are distinguishable by the angle 0 between the Co moment and the symmetry axis at that site. Two peaks with the intensity ratio of 3:1 should be observed in the spin echo spectra of ⁵⁹Co in the RCo₂ with the <111> easy axis, whereas one resonance is expected for the compound with the <100> easy axis. The observed spin echo spectra are shown. It was concluded that all spectra are due to ⁵⁹Co in magnetic domains or in domain walls from the observations of frequency-shifts and intensity-changes under applied magnetic fields up to 50kOe. Possible mechanisms to explain the large anisotropy in hyperfine fields are discussed. (UK)