  The transport and magnetic properties of correlated La{0.53}Sr{0.47}MnO{3}
ultrathin films, grown epitaxially on SrTiO{3}, show a sharp cusp at the
structural transition temperature of the substrate. Using a combination of
experiment and theory we show that the cusp is a result of resonant coupling
between the charge carriers in the film and a soft phonon mode in the SrTiO{3},
mediated through oxygen octahedra in the film. The amplitude of the mode
diverges towards the transition temperature, and phonons are launched into the
first few atomic layers of the film affecting its electronic state.
