  The hyperfine splitting of the ground state of selected B-like ions within
the range of nuclear charge numbers $Z=49-83$ is investigated in detail. The
rigorous QED approach together with the large-scale configuration-interaction
Dirac-Fock-Sturm method are employed for the evaluation of the
interelectronic-interaction contributions of first and higher orders in $1/Z$.
The screened QED corrections are evaluated to all orders in $\alpha Z$ by using
an effective potential. The influence of nuclear magnetization distribution is
taken into account within the single-particle nuclear model.
