9 Acknowledgments PBRM model an excellent candidate to explore the prop- erties of the 3D Anderson model at criticality at a low computational cost. We want to stress that for both models at criticality, the PBRM model and the 3D Anderson model, we found the universal behavior ρ (ln T ) ∝ T M $^{2}$/ 2 for T ≪ 1, that we tested here for M = 1 and M = 2. Moreover by the use of the PBRM model with β = 2 (not shown here) we have already verified that the more general expres- sion ρ (ln T ) ∝ T βM $^{2}$/ $^{2}$, derived from38 w ( T ) ∝ T βM $^{2}$/ 2 − 1 with 0 < T < 1, holds. We emphasize that, even though we used a scattering setup where the leads are attached perfectly to sites at one side of the sample, our conclusions are not restricted to this topology. 46 Finally, we recall that we concentrate here on the case of a small number of single-channel attached leads (up to ten). 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