The K-shell ionization cross sections. σkl, have been measured for the natural 60Nd, 62Sm, 65Tb, 69Tm and 73Ta targets for incident proton energies of 0.8–3.8 MeV and for 64Gd and 73Ta targets for incident deuteron energies of 0.9–3.2 MeV. The absolute σkl values have been determined by normalization to the known Coulomb excitation cross sections σc of the nuclear collective states of the target nuclei. The experimental results are compared with the predictions of the SCA and PWBA models including the electron binding, Coulomb repulsion and relativistic corrections. The σHe4σD and σHσD ratios of the ionization cross sections have been also compared with the SCA model predictions by using our earlier and literature results for protons and alpha particles for Gd and Ta targets.