Ce- and Yb-based Kondo semiconductors

Kondo semiconductors are a class of strongly correlated f-electron materials whose low-energy excitations exhibit a (pseudo)gap at low temperatures. The significant difference between the pseudogap in orthorhombic CeNiSn and CeRhSb and the real gap in cubic Ce(3)Bi(4)Pt(3) and YbB(12) is highlighted by a comparison of transport properties. Low-temperature measurements of the magnetoresistance, Hall coefficient and specific heat of CeNiSn have revealed a field-induced excitation of the coherent low-carrier state. A systematic study of CeNi(1-x)T(x)Sn (T = Co, Cu and Pt) has shown that the residual carriers in CeNiSn are immobilized by 1% substitution irrespective of the substitutes. Further substitution with 5% Cu induces a magnetic instability at T = 0. (C) 1998 Elsevier Science B.V. All rights reserved.