CoFeF5(H2O)2 and NiFeF5(H2O)2 which crystallize with the inverse weberite structure were investigated as a function of temperature by Mössbauer spectroscopy and then compared to isotypic compounds as ZnFeF5(H2O)2, MnFeF5(H2O)2 and Fe2F5(H2O)2. An external magnetic field was applied to these compounds below their magnetic ordering temperature: the different magnetic behaviour is discussed in terms of frustration and cationic local anisotropy. © 1988.