Strongly coupled charge-density wave transition in single-crystal Lu<SUB>5</SUB>Ir<SUB>4</SUB>Si<SUB>10</SUB>

We report the observation of a strongly coupled first-order charge-density wave (CDW) transition in a high-quality single crystal of the intermetallic compound Lu<SUB>5</SUB>Ir<SUB>4</SUB>Si<SUB>10</SUB>. The first-order nature is ascertained by a very narrow and huge cusp (360 J/mol K) in the specific heat. The susceptibility and the resistivity also show sharp jumps at the transition T<SUB>CDW</SUB>=83 K. The periodic lattice distortion associated with the CDW is exemplified by the formation of x-ray superlattice reflections along the tetragonal c&#8594; axis with q&#8594;&#8776;(0,0,3/7) (T&lt;83 K). Although our results are in accordance with a quasi-one-dimensional CDW scenario, the first-order transition suggests a strong interchain coupling. We propose Lu<SUB>5</SUB>Ir<SUB>4</SUB>Si<SUB>10</SUB> as a paradigm of such strong-coupling CDW systems