Electromagnetically Induced Transparency and slow light in media with Rydberg Excitons

We show that the Electromagnetically Induced Transparency (EIT) is possible in a medium exhibiting Rydberg excitons and indicate the realistic parameters to perform the experiment. The calculations for a Cu${}_2$O crystal are given which show that in this medium due to large group index one could expect slowing down a light pulse by a factor about ${10}^4$.