Transport properties of Ce2Co7B3 in magnetic field

Thermopower S, resistivity p and magnetization M of Ce2Co7B3 have been measured in magnetic fields up to 15 T at temperature range from 2 to 1000 K. The magnetic field dependence of S(H) and p(H) changes drastically at spin-flop critical field H-S = 6.0T in 4.2 K. A very large negative magnetoresistance is observed, 35% in 15 T at 4.0 K, suggesting large spin-spin interaction between s and d electrons. Magnetic phase transitions in temperature and field are experimentally obtained, a magnetic phase diagram is established. The S(T) measured up to 1000 K suggests that a DOS peak exists at 250 K apart from Fermi level (epsilon(F)) in energy. Below H-S, a negative peak exists on the S(T) curve around 20 K, which disappears suddenly at H-S. The negative peak is estimated coming froth a super-zone boundary on epsilon-k curve caused by anti-ferromagnetic periodicity. The DOS below and above H-S have been estimated from experimental S(T) in terms of Mott's two band s-d scattering model.