Anode material for a fuel cell which is to be operated at a high temperature above 700.degree. C., which anode material is a porous composite material with a heterogeneous phase of solid materials which is formed by two reticular systems which penetrate each other in interlaced manner of particles connected by sintering, namely a first reticular system of ceramic material, and also a second reticular system of metallic material for the purpose of bringing about redox processes and an electrical conductivity, characterized in that the first reticular system is composed of large and small ceramic particles (10, 11) with average diameters d.sub.50 greater than 5 .mu.m or smaller than 1 .mu.m respectively, in that 50% to 80% of the first reticular system is formed from the large ceramic particles (10), and in that a composition of the anode material to be used is given by values which are selected by means of samples of this material and a test method, wherein the test method includes at least one redox cycle, an irreversible change in length of the selected sample adopting in this a value smaller than 0.002, preferably smaller than 0.0005, and the following measurements and evaluations being carried out per redox cycle at a temperature which is at least the same as the operating temperature of the fuel cell: A linear elongation of the sample is measured in the oxidized state of the second reticular system and a value L.sub.1 is determined. The second reticular system is reduced, is oxidized again after at least one hour, and a value L.sub.2 of the linear elongation is determined for the newly oxidized state. One obtains the specific value of the irreversible change in length as the ratio (L.sub.1-L.sub.2):L.sub.1.