We report the measurements of the $CP$-violating parameters in $B_s^0 to D_s^{mp} K^{pm}$ decays observed in $pp$ collisions, using a data set corresponding to an integrated luminosity of $3.0,text{fb}^{-1}$ recorded with the LHCb detector. We measure $C_f = 0.73 pm 0.14 pm 0.05$, $A^{Delta Gamma}_f = 0.39 pm 0.28 pm 0.15$, $A^{Delta Gamma}_{overline{f}} = 0.31 pm 0.28 pm 0.15$, $S_f = -0.52 pm 0.20 pm 0.07$, $S_{overline{f}} = -0.49 pm 0.20 pm 0.07$, where the uncertainties are statistical and systematic, respectively. These parameters are used together with the world-average value of the $B_s^0$ mixing phase, $-2beta_s$, to obtain a measurement of the CKM angle $gamma$ from $B_s^0 to D_s^{mp} K^{pm}$ decays, yielding $gamma = (128,_{-22}^{+17})^circ$ modulo $180^circ$, where the uncertainty contains both statistical and systematic contributions. This corresponds to $3.8,sigma$ evidence for $CP$ violation in the interference between decay and decay after mixing.
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