We have measured the electrical resistivity and the magnetoresistance (MR) of the single-component molecular metal [Ni(tmdt)2] at high magnetic fields. The temperature dependence of the resistivity shows a T2 behavior up to 30 K, but this is difficult to explain in terms of the simple Fermi liquid picture. We find a highly isotropic positive MR below 4.2 K which exhibits a metal-insulator behavior. These results are discussed in terms of the Zeeman effect in the presence of spin-orbit coupling on the Ni sites.