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Optical spectroscopy is an excellent tool to study the dynamics of heavy fermions and their characteristic energy scales: the Drude response (with its enormously enhanced transport relaxation time) and the so-called hybridization gap (a signature of the peculiar band structure due to electronic interactions) are of particular interest. Here we present the electrodynamic response of the heavy-fermion compound UNi2Al3 in a very wide frequency range, as obtained from a combination of different microwave and optical techniques. At temperatures below 30K, we find a strongly frequency-dependent optical conductivity: the Drude roll-off occurs below 20GHz, but at frequencies around 300GHz (=10cm-1, i.e. much lower than typical hybridization gaps), we observe another band of substantial conductivity (comparable to the dc conductivity). We discuss these results in comparison with our previous studies on UPd2Al3, and we also address the anisotropy of the conductivity. |
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