Interference between $E1$ and $M1$ transition amplitudes on the $H$ to $C$ transition in ThO

Calculations of Stark interference between $E1$ and $M1$ transition amplitudes on the $H^3{\mathrm{\Delta }}_1$ to $C^1\mathrm{\Pi }$ transition in ThO is performed. Calculations are required for estimations of systematic errors in the experiment for electron electric dipole (eEDM) moment search due to imperfections in laser beams used to prepare the molecule and read out the (eEDM) signal.