We have grown low-resistive and n-type beta-FeSi2 single crystals by the temperature gradient solution growth (TGSG) method using Ni-doped Zn solvent. These crystals were obtained at the Ni concentrations between 0.05 and 0.5 wt%. Above the Ni concentration of 1.0 wt%, nickel silicides were preferably grown. The resisitivity of the Ni-doped crystals was 0.2-0.5 Omega cm at room temperature (RT). The electron concentration and Hall mobility at RT were (5-6) x 10(18) cm(-3) and 3-6 cm(2)/V s, respectively. We also determined the ionization energy of 26-60 meV for the Ni impurity in beta-FeSi2. (c) 2006 Elsevier B.V. All rights reserved.