Energy spectra, spectroscopic factors and electromagnetic moments of the low-lying states of 120-124Sb have been calculated in the framework of the interacting boson-fermion-fermion model, and compared with the experimental values. It was found that the collectivity has a significant effect on the energy splitting of the multiplets. The dynamical boson-fermion interaction leads to a smoothing of the energy splitting, while the exchange interaction tends to cause a fourth order polynomial splitting in the E* versus J(J+1) plot. The smoothing of the energy splitting can be interpreted in a quasiparticle picture as the lengthening of the range of the p-n effective interaction. The collective and single particle effects have comparable contributions in the electromagnetic moments, and the single particle part of the transfer operator determines the spectroscopic factors
