We demonstrate that Zeeman ground-state spin levels in Nd3+:YVO4Nd3+:YVO4 provides the possibility to create an efficient ΛΛ- system for optical pumping experiments. The branching ratio R in the ΛΛ-system is measured experimentally via absorption spectroscopy and is compared to a theoretical model. We show that R can be tuned by changing the orientation of the magnetic field. These results are applied to optical pumping experiments, where significant improvement is obtained compared to previous experiments in this system. The tunability of the branching ratio in combination with its good coherence properties and the high oscillator strength makes Nd3+:YVO4Nd3+:YVO4 an interesting candidate for various quantum information protocols.