Electronic transport measurements of Ag/3,4,9,10-perylenetetracarboxylic dianhydride In/Si(001) heterostructures demonstrate that when the structure temperature approaches the In melting point a current-voltage characteristic changes from rectifying to ohmic. The synchrotron radiation photoemission investigation of the 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) layers of the same thickness grown on In in the same temperature range show strong In diffusion throughout the PTCDA layers as thick as 1 mum. The formation of In-related coordination compound appears to be limited to the region near the In/PTCDA interface.