Anomalies In The Antiferromagnetic Phase On Ceirsi3

In order to investigate a magnetic ground state and electrical structure of CeIrSi3, we have performed the electrical resistivity and specific heat measurements at low temperatures and magnetic fields. In the antiferromagnetic phase, two anomalies are found. One is a weak hump with a broad hysteresis in the resistivity at 0.6K, which implies a first-order phase transition. The other is an "N" shaped transvers-magnetoresistance. A complicated hysteresis is accompanied with the magnetoresistance. Theses anomalies disappear by applying a slight pressure. The magnetic and electronic states of CeIrSi3 are complicated and sensitive to pressure.