TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preparation (Claimed): Preparation of (I) comprises: either (a) preparing a soil containing salts of nitrates of aluminum, magnesium, rhodium and/or nickel, a surfactant and the solvents such as water, ethanol and ammonia; (b) dipping a substrate in the prepared soil; (c) drying the impregnated substrate of soil to obtain a gelled composite material comprising a substrate and a gelled matrix; (d) calcination of the composite material gelled step (c) to a temperature of 450 degrees c-1100 degrees c, preferably at a temperature of 900 degrees C, and (e) reduction of the calcined material; or (a1) preparation of a sol comprising nitrate salts of aluminum, magnesium, rhodium and/or nickel, a surfactant and the solvent such as water, ethanol and ammonia; (b1) atomization of soil in contact with a stream of hot air to evaporate the solvent and form micron powder; (c1) calcining the powder at 450-1100 degrees C, preferably 900 degrees C; and (d1) reduction of the calcined material. Preferred Components: The chemical interaction is electronic interactions, epitaxy interactions and/or partial encapsulation interactions. The arrangement is in spinel phase. The metal particles are rhodium, platinum, palladium and/or nickel. The crystallites have a mean equivalent diameter of 10-22 nm, preferably 15-20 nm, and metal particles have a mean equivalent diameter of 1-10 nm, preferably less than 5 nm. The arrangement of crystallites is a compact hexagonal or cubic stack centered in which each crystallite is contacting with almost 12 other crystallites in a 3-dimensional space. The catalyst comprises a substrate and a film comprising arrangement of crystallites and the active phase. The catalyst comprises granules comprising arrangement of crystallites and the active phase. The substrate is a ceramic or metal or ceramic coated metal surface. EXAMPLE - Rhodium-aluminum-magnesium was sprayed on the substrate followed by calcination of the powder in air at 1000 degrees C for 4 hours to produce spherical droplets with a diameter less than 5 mu m, preferably 100 nm to 2 mu m. The droplets were porous and consist of carrier particles with a diameter of 20 nm. The thin films obtained by spraying a substrate on the soil and the powders obtained by atomization of soil were aged under hydrothermal conditions, at a temperature of 900 degrees C for 100 hours under an atmosphere rich in water vapor and nitrogen (where the molar ratio of water vapor on nitrogen is 3). The ultra-divided micro structure deposits calcined at 1000 degrees C changed little during the hydrothermal aging to obtain the catalyst.