Semiconducting behaviour in CeT2Al10 (T=Fe and Ru)

We present results of the magnetic susceptibility, electrical resistivity and thermopower for CeT2Al10 (T=Fe and Ru) crystallizing in the orthorhombic YbFe2Al10-type structure. The magnetic susceptibility for CeFe2Al10 shows a maximum at 70 K which is a characteristic of a valence fluctuation system. The electrical resistivity below 20 K exhibits semiconducting behaviour with an energy gap of 15 K. On the other hand, CeRu2Al10 displays Curie-Weiss behaviour of Ce3+ in the susceptibility down to 30 K, and undergoes an antiferromagnetic transition at TN=27 K. The semiconducting behaviour of the resistivity between 70 K and 30 K is described by a gap of 50 K. On cooling below TN, however, the resistivity exhibits a peak at 23 K and falls down. The thermopower shows two maxima at 22 K and 6 K. These findings suggest that the magnetic order induces a semiconductor-to-metal transition in CeRu2Al10.