A remarkable change has been evident when analyzing the thermal variation of reflectivity by plotting the absolute reflectivity value at 550 nm against temperature (Figure , right). The absolute reflectivity curve shows a gradual decrease upon lowering the temperature from 300 K to 10 K with a minimum at around 60 K. The nature of the curve implies a spin-state switching occurring between HS and LS states at around 120 K, where the magnetic measurements of the powder sample also indicate a comparable T1/2 value. A similar behaviour as that of the cooling curve was observed upon heating the sample from 10 to 300 K. The findings of optical studies are in agreement with magnetic studies, confirming the occurrence of reversible spin-crossover phenomenon.