We report a study of a single-crystal La 3 Co 4 Sn 13 by means of the specific heat and 59 Co nuclear magnetic resonance (NMR) spectroscopy. A first-order phase transition with a marked peak at T * 152 K has been discerned by the specific heat measurement. The observed transition has been connected to a structural change from a simple cubic to a body-centered-cubic superstructure with crystallographic cell doubling, accompanied by the Fermi surface reconstruction. Indeed, NMR observations clearly indicate a significant change in the local electronic characteristics across this phase transition. The spin-lattice-relaxation rate measurement further provides an estimate of Co 3d Fermi-level density of states N d (E F ), revealing a visible reduction in N d (E F ) in the low-temperature phase. This finding essentially associated with the partially gapped Fermi surfaces would be appropriate for the isostructural analog of Sr 3 Ir 4 Sn 13 , which has been claimed to possess charge-density-wave (CDW) behavior with a three-dimensional crystallographic structure.

We report an observation of a first-order phase transition in Ce 3 Co 4 Sn 13 by means of the specific heat, electrical resistivity, Seebeck coefficient, and thermal conductivity, as well as 59 Co nuclear magnetic resonance (NMR) measurements. The phase transition has been evidenced by marked features near T o 155 K in all measured physical quantities except for magnetic susceptibility. This excludes a magnetic origin for the observed phase transition. In addition, x-ray diffraction results below and above T o confirm the absence of a structural change, suggesting that the peculiar phase transition is possibly related to an electronic origin and/or electron-lattice coupling such as the formation of a charge density wave (CDW). As a matter of fact, the disappearance of the double-peak feature of 59 Co NMR central lines below T o can be realized as the spatial modulation of the electric field gradient due to incommensurate CDW superlattices. Also, a distinct peak found in the spin-lattice relaxation rate near T o manifests a phase transition and its feature can be accounted for by the thermally driven normal modes of the CDW. From the NMR analyses, we obtained a consistent picture that the change of electronic structures below T o is mainly due to the weakening of p-d hybridization. Such an effect could result in possible electron-lattice instability and, thus, the formation of a CDW state in Ce 3 Co 4 Sn 13 .

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