(a) The measured σ₁(ω) at 150 K (thick black line) in a wide spectral range for CaCo₂As₂, fitting with the Drude–Lorentz model (thin red line). The optical conductivity of CaCo₂As₂ can be separated into temperature-dependent and -independent parts. The temperature-independent part consists from the incoherent broad Drude term σ_b (magenta line), and two Lorentzian oscillators at higher frequencies (orange and dark yellow lines). The sum of the three contributions results in the light gray shaded area. The unshaded area below the curves is temperature dependent and can be described by a single Drude term σ_n (blue line). Temperature evolution of σ_n for CaCo₂As₂ is shown in panel (b). The thin lines through the data are fits with a single Drude term.