Hidden order pseudogap in URu$_2$Si$_2$
  Through an analysis and modeling of data from various experimental techniques, we present clear evidence for the presence of a hidden order pseudogap in \U in the temperature range between 25 K and 17.5 K. Considering fluctuations of the hidden order energy gap at the transition as the origin of the pseudogap, we evaluate the effects that gap fluctuations would produce on observables like tunneling conductance, neutron scattering and nuclear resonance, and relate them to the experimental findings. We show that the transition into hidden order phase is likely second order and is preceded by the onset of non-coherent hidden order fluctuations. 
J.T. Haraldsen, Y. Dubi, N.J. Curro, and A.V. Balatsky
cond-mat.str-el cond-mat.mtrl-sci