Kondo insulator is one of the systems which got particular interest, but
not yet understood well. Metal-insulator (MI) transition by doping in
these systems is one of the examples poorly understood. U₃M₃Bi₄ forms in
the same crystal structure with Ce₃Pt₃Bi₄, which is well known Kondo
insulator. We have succeeded in synthesizing new single crystals of
U₃M₃Bi₄, where M = Rh, Ni, with metallic Kondo lattice and
semiconducting behaviors, respectively. It provides the opportunity to
investigate metal-insulator transition in Kondo insulating system without
affecting the crystal structure.