  The rate of the non-perturbative decay of a 't Hooft - Polyakov monopole in
an external electric field into a dyon and a charged fermion is calculated. The
subleading semiclassical prefactor is presented for the first time for this
process. The leading exponential factor is shown to be in full agreement with
the previous results derived in a different technique. Analogous treatment is
shown to hold for the two-fermionic decay of the lightest bound state in
Thirring model, allowing one to restore the "effective meson - fermion vertex".
