  We study effects of Coulomb interactions between localised states in a
potential barrier by measuring resonant-tunneling spectra with a small bias
applied along the barrier. In the ohmic regime the conductance of 0.2um--gate
lateral GaAs microstructures shows distinct peaks associated with individual
localised states. However, when an electric field is applied new states start
contributing to the current, which becomes a correlated electron flow through
two interacting localised states. Several situations of such correlations have
been observed, and the conclusions are confirmed by calculations.
