An experiment on testing the time-reversal symmetry in the emission of a mixed $E2\text{−}M1$ Mössbauer γ-transition in ${}^{171}\mathrm{Yb}$ has been carried out. The imaginary part of the ratio of a reduced multipole matrix element has been measured by observing the appearance of the additional linear polarization of γ-rays transmitted through the system of resonant filters. The application of this system has made it possible to exclude corrections for the spurious phase that emerges due to the interaction of a $\gamma$-ray with surrounding atomic electrons. In the experiment, the phase $\sin (\Delta \eta )=(6.3\pm 4.6)\times {10}^{-5}$ and the coefficient of self-compensation of the Faraday rotation $k=-(1.1\pm 1.0)\times {10}^{-4}$ have been observed. The limit $\Delta \eta$ has been found equal to $10.9\times {10}^{-5}$. This is the accuracy of determination of the $T$-invariance retention.

• Received 15 November 2005

DOI:https://doi.org/10.1103/PhysRevC.76.045503