Abstract: The ¹⁹⁸Au@Au sample was produced via ¹⁹⁷Au(n,γ)¹⁹⁸Au reaction. The relative activities of 412 keV characteristic γ-ray from the ¹⁹⁸Au@Au sample were measured at T=293 K and T=12 K, alternately. The β^--decay half-life of ¹⁹⁸Au in a Au metallic environment was observed to be longer by (0.4±0.7)% at room temperature (T=293 K) and by (4.0±0.7)% when the metal was cooled to T= 12 K, both compared to the literature value of T_1/2 =(2.694 3±0.000 8) d. The result is consistent qualitatively with, but clearly lower than, the prediction of the Debye plasma model.