Origin of quadrature scaling of strange-metal magnetoresistance

In BaFe2(As1-xPx)2 and overdoped La2-xSrxCuO4 and Tl2Ba2CuO6+d, the magnetoresistance follows $\rho(H,T) - \rho_{0} \sim \sqrt{(\alpha k_{B} T)^2 + (\gamma \mu_{B} H)^2}$ with $\gamma/\alpha$ of order one, including in orbital geometry. Derive this form and the measured ratio $\gamma/\alpha$ from a microscopic model.

A model calculation of $\rho(H,T)$ reproducing the scaling form, the ratio $\gamma/\alpha$ and its angle dependence in one of these materials.