  We study $K^+$-meson production in $\gamma{A}$ interaction at energies below
the reaction threshold in free space. The Thomas-Fermi and spectral function
approaches are used for the calculations of the production process. It is found
that the measurement of the differential spectra may allow to reconstruct the
production mechanism and to investigate the dispersion relations entering the
production vertex. It is shown that the contribution from secondary pion
induced reactions to the total kaon photoproduction is negligible for
$E_\gamma{<}$1.2 GeV so that strangeness production at low energies is
sensitive to the nuclear spectral function.
