[en] Formation and dissociation of acceptor-donor-pairs in silicon are studied by the perturbed angular correlation method (PAC) using radioactive In(→Cd) probe atoms. In Sb-doped Si a stable In(→Cd)-Sb complex is observed at temperatures below 800 K, which is characterized by a strongly temperature dependent axially symmetric electric field gradient (EFG). The data indicate a thermally activated repopulation of the Cd-acceptor levels. In Cz-Si the two observed different EFGs correspond to two different local configurations of the In(→Cd)acceptor trapped at the oxygen-based Thermal Donor. At 700 K the measurements reveal a local rearrangement of this complex, at 900 K the acceptor-donor dissolves. (author) 6 figs., 2 tabs., 7 refs