SrMo0.9Co0.1O3.4 oxide has been prepared, characterized and tested as anode material in single solid-oxide fuel cells (SOFC), yielding output powers close to 800 mW cm(-2) at 850 degrees C with pure H-2 as a fuel. This excellent performance is accounted for the results of an "in-situ" neutron powder diffraction (NPD) experiment, at the working conditions of a SOFC, showing the presence of a sufficiently high oxygen deficiency, with large displacement factors for oxygen atoms that suggest a large lability and mobility, combined with a huge metal-like electronic conductivity, as high as 386 S cm(-1) at T = 50 degrees C. Besides, the oxidation of the perovskite gives rise to a new oxygen deficient scheelite-like phase with formula SrMo0.9Co0.1O4-delta with Mo(VI), which has been studied by NPD and thermal analysis as far as crystal structure and composition are concerned. An adequate thermal expansion coefficient for both (oxidized and reduced) phases, an excellent reversibility upon cycling in oxidizing reducing atmospheres and a good chemical compatibility with the electrolyte (La0.8Sr0.2Ga0.83Mg0.17O3-delta; LSGM) make this oxide a good candidate for anode in intermediate-temperature SOFC (IT-SOFCs). (C) 2014 Elsevier B.V. All rights reserved.