  We report here the electrical transport and magnetic properties of the newly
synthesized quaternary Heusler compound CoFeTiSn and CoFeVGa. We observe a
striking change in the electronic transport properties of CoFeTiSn as the
system undergoes the paramagnetic to ferromagnetic transition. While the sample
shows an activated semiconducting behaviour in the paramagnetic phase, it turns
abruptly to a metallic phase with the onset of ferromagnetic transition. We
have compared the system with other Hesuler compounds showing similar anomaly
in transport, and it appears that CoFeTiSn has much similarities with the
Fe$_2$VAl compound having pseudogap in the paramagnetic phase. In sharp
contrast, CoFeVGa shows a predominantly semiconducting behaviour down to 90 K,
below which it shows a window of metallic region. Both the compositions show
negative Seebeck coefficient varying linearly with temperature. The value of
the Seebeck coefficient of CoFeTiSn is comparable to that of many Heusler
alloys identified as potential thermoelectric materials.
