We calculate energies and hyperfine structure constants A and B for low-lyi
ng levels of Yb-173. The latter is treated as a two-electron atom. To accou
nt for valence-valence correlations the configuration interaction method is
used. Valence-core correlations are accounted for within the many-body per
turbation theory which is used to construct effective two-electron operator
s in the valence space.