The development of new transition metal complexes (TMCs) sensing materials, based on di-rhodium (II,II) complexes with a lantern structure, is investigated. Specifically, in this work is reported a study carried out with the Rh2(form)4 complex having the formamidinate (form = N.N-p-tolylformamidinate anion) bridging ligand in the equatorial positions. Thick films of the complex have been deposited on interdigitated alumina substrate and their electrical characteristics have been evaluated. Rh2(form)4 behaves as a p-type semiconductor, showing a large decrease in forward and reverse current in presence of ammonia vapors in air. The preliminary results reported promise a practical application of the developed devices in the breath analysis for clinical diagnostics.