Presentation #100.48 in the session AGN.
High-redshift MeV blazars are some of the most extreme sources in the Universe. With jet power exceeding 1047 erg s-1, they are fueled by billion solar masses black holes and are found when the Universe was only two billions years old. These sources are of great astrophysical importance as they can provide us crucial information about the origin and growth of supermassive black-holes in the early Universe. Detection in the hard X-rays is desired to find the most powerful objects of this class and understand their properties. Using the superb capabilities of the Nuclear Spectroscopic Telescope Array (NuSTAR), we have identified six new MeV blazars, all lying beyond redshift 4, at the peak of these sources cosmic evolution. In this talk, I will present the latest results on high redshift blazars with NuSTAR and discuss their implications for the larger population of extreme jets and supermassive black holes.