The low-temperature electrical and magnetic properties of TaSe2 and NbSe2

NbSe2 has been reported to have an anomalous sign change in the Hall coefficient at low temperatures. In this paper it will be shown that the sign change is associated with a magnetic ordering. In addition, electrical and magnetic studies have been carried out on TaSe2, and a similar anomalous sign change is observed in the Hall coefficient at about 90°K. A small degree of magnetic ordering is also present in this compound near the temperature at which the Hall coefficient begins the rapid change from p- to n-type.