  We measured thermal conductivity, k, thermoelectric power, S, and dc electric
conductivity, sigma, of La_{5/8-x}Pr_{x}Ca_{3/8}MnO_{3}, showing an intricate
interplay between metallic ferromagnetism (FM) and charge ordering (CO)
instability. The change of k, S and sigma with temperature (T) and x agrees
well with the effective medium theories for binary metal-insulator mixtures.
This agreement clearly demonstrates that with the variation of T as well as x,
the relative volumes of FM and CO phases drastically change and percolative
metal-insulator transition occurs in the mixture of FM and CO domains.
