NARROW-GAP SIGNATURE OF FEXCO1-XSI SINGLE-CRYSTALS

Heat capacity, resistance, and magnetic susceptibility have been measured on FeSi, Fe0.90Co0.10Si, Fe0.10Co0.90Si, and CoSi single crystals. From resistance experiments, the activation energy (DELTA) shows a small variation from DELTA almost-equal-to 310 K in FeSi to DELTA almost-equal-to 325 K for the Fe0.90Co0.10Si compound. For the 90% Co compound the gap signature disappears completely. Heat capacity experiments performed in the temperature range 1.5 K < T < 20 K reveal an increasing Sommerfeld coefficient (gamma) with increasing Co content. A comparison is made with the hybridization gapped material Ce3Bi4Pt3.