Hyperfine structure and $K$-doubling in RaOCH${}_3$ molecule

RaOCH${}_3$ molecule is one of the most sensitive systems for the electron electric dipole moment ($e$EDM) searches. Its hyperfine and $K-$doubling structure in the external electric field is of key importance for preparing and interpreting the experiment. We propose the method for calculation the symmetric top molecules and applied it for RaOCH${}_3$. Hyperfine structure, $K-$doubling and sensitivity of the molecule to $e$EDM in the external electric field were calculated.