Local structure in the hidden order phase of URu2Si2

URu2Si2 is one of the most actively studied materials exhibiting unconventional behaviour due to electronic correlations. The mystery of this compound is the nature of the so-called `hidden order' state, which sets in below 17.5 K. This transition is characterised by an enormous change in entropy (~0.2R ln2). A small `parasitic' antiferromagnetic order sets in in the HO phase, but its ordered moment is far too small to explain the change in entropy. The nature of the order parameter is still uncertain, despite intensive theoretical and experimental efforts. Some studies have observed a distortion of the tetragonal lattice in the hidden order phase, but the effect is highly sample dependent, whereas other signatures of hidden order are not. We propose to use PDF analysis to study the local structure in URu2Si2 to see if there might be a hidden lattice distortion as well as hidden order