Fig. 1: Scale invariance in the resistivity of Ba(Fe_1/3Co_1/3Ni_1/3)₂As₂.

a Temperture dependence of resistivity for Ba(Fe_1/3Co_1/3Ni_1/3)₂As₂ in the configuration of B ∥ ab, B ⊥ I ∥ ab. Upper inset: crystal structure for Ba(Fe_1/3Co_1/3Ni_1/3)₂As₂ (ref. ⁴⁶). Lower inset: Δρ(T) = ρ(T) − ρ(0)) as a function of T at B = 0 T for Ba(Fe_1/3Co_1/3Ni_1/3)₂As₂. A dashed line is a guide to the eye to highlight quasi-linear-in-T dependence of resistivity. b Magnetic field dependence of ΔR(B)/R(0) ≡ (R(1.31 K, B) − R(1.31 K, 0))/R(1.31 K, 0) at T = 1.31 K. A red dashed line is a guide to the eye to highlight sublinear-in-B behavior of magnetoresistance. Inset: angular dependence of magnetoresistance at T = 550 mK and B(∥c ⊥ I) = 35 T. c Inelastic scattering rate ℏ/τ as a function of \(\Gamma =\sqrt{{({k}_{{\rm{B}}}T)}^{2}+{(\eta {\mu }_{{\rm{B}}}B)}^{2}}\), with η = 0.67, suggestive of a universal scale invariance in the scattering mechanism in Ba(Fe_1/3Co_1/3Ni_1/3)₂As₂. A blue sold line is a linear fit to data using ℏ/τ = AΓ with A = 1.8. d Temperature dependence of anisotropy of magnetoresistance between Δρ(B ∥ c) and Δρ(B ∥ ab ⊥ I; sample #1) and between Δρ(B ∥ c) and Δρ(B ∥ ab ∥ I; sample #2) at B  = 14 T, showing lack of anisotropy in the scattering rate.