Magnetism and electronic correlations in the iron aluminides R Fe 2 Al 10 ( R = Y, Yb)

YFe 2 Al 10 and YbFe 2 Al 10 are new additions to the currently investigated rare‐earth ( R ) series of compounds RT 2 Al 10 in which T is Fe, Ru, or Os. Unusual physical properties are drawing considerable attention to this group of compounds. Intriguingly, very small moments order in CeRu 2 Al 10 at as high as 27 K, whereas CeFe 2 Al 10 is a Kondo insulator with very strong hybridization of the Ce magnetic moments and no magnetic ordering at all. Here we present the first results of two further iron‐based compounds YFe 2 Al 10 and YbFe 2 Al 10 as a timely contribution to the knowledge of the physics at work in this system. In YFe 2 Al 10 we find signatures of correlated electrons and the low‐temperature results of specific heat, magnetic susceptibility and electrical resistivity are indicative of ferromagnetic quantum criticality. In YbFe 2 Al 10 localized f‐electron spins of Yb become involved in correlations with a moderately enhanced electronic specific heat that classifies it as a non‐ordered heavy‐fermion compound. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)