  We report that CaMn$_7$O$_{12}$ is a new magnetic multiferroic material. The
appearance of a ferroelectric polarization coinciding with the magnetic phase
transition ($\sim90$ K) suggests the presence of ferroelectricity induced by
magnetism, further confirmed by its strong magnetoelectric response. With
respect to other known magnetic multiferroics, CaMn$_7$O$_{12}$ displays
attractive multiferroic properties, such as a high ferroelectric critical
temperature and large polarization. More importantly, these results open a new
avenue to search for magnetic multiferroics in the catalogue of doped oxides.
