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Given the challenges in experimental studies of uranium, the heaviest naturally occurring metal, we present first-principles calculation for the spin-dependent transport. Showing the largest atomic spin-orbit coupling we explore the ability of various crystal phases to maximise the charge to spin conversion using a full relativistic Korringa-Kohn-Rostoker Greens function method. The transport theory is based on a semi classical description where intrinsic and extrinsic, skew scattering, contributions can be separated easily. In addition to the various crystal phases we analyse the effect of substitutional impurities for γ, hcp, as well as the α-phase. We predict a very high, 10 4 (Ωcm) −1 , spin Hall conductivity for the meta-stable hcp-U phase, a giant value 5 times larger than for the conventional spin Hall material Pt. We estimated an efficiency of charge-to-spin current conversion of up to 30%. The spin diffusion length, a crucial parameter in any application, is predicted to be in the range from 3 − 6.5nm, compatible with other charge-to-spin conversion materials. Relating our work to the sparse experimental results, our calculations suggest a γ phase in the thin film rather than the experimentally expected α phase.

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In response to the comment by Zhu and Berakdar (arXiv:1207.3457) that the physical system considered by them in their previous work [Ding et al., PRB 84, 115433 (2011)] is conceptually different from ours in the appendix of our latest paper [Zhou and Wu, arXiv:1206.3435], we show why they are relevant and further point out conceptually the problems in their work. We also point out that the main supporting arguments in their comment are incorrect.