Kondo Lattice Behavior in the Ordered Dilute Magnetic Semiconductor   Yb_{14-x}La_xMnSb_{11}
  We report Hall, magnetic, heat capacity and doping studies from single crystals of Yb_14MnSb_11 and Yb_13.3La_0.7MnSb_11. These heavily doped semiconducting compounds are ferromagnetic below 53 K and 39 K respectively. The renormalization of the carrier mass from 2 me near room temperature to 15 me at 5 K, plus the magnetic evidence for partial screening of the Mn magnetic moments suggest that these compounds represent rare examples of an underscreened Kondo lattice with T_K = 350 K. 
B.C. Sales, P. Khalifah, T. P. Enck, E. J. Nagler, R. E. Sykora, R.   Jin & D. Mandrus