Rate for positronium decay to five photons

In this report we calculate ${\Gamma }_5$, the rate for orthopositronium to decay to five photons. We find that ${\Gamma }_5=[0.0189(11\left)\right]{\alpha }^2{\Gamma }_{\mathrm{Lo}}$, where ${\Gamma }_{\mathrm{Lo}}$ is the lowest-order orthopositronium decay rate. The relevance of our result to the experimental situation is discussed.