Negative thermal expansion in nanostructured intermediate valence $\text{YbAl}_3$

Interest in the strongly correlated electron system YbAl 3 has been recently renewed by the observation of a breakdown of coherence effects and Fermi liquid behavior when the alloy's particle size is reduced to around 11 nm. Powder diffraction measurements using neutron and synchrotron radiation allow us to estimate the thermal expansion of the nanostructured YbAl 3 . A region of negative thermal expansion in the nanostructured material occurs at higher temperatures compared to that of bulk YbAl 3 . This shows that the reduction in the size of YbAl 3 not only affects electronic properties, but also the lattice dynamics of this material.