089045

Active galactic nuclei openParAGNclosePar comma which represent the growing phase of supermassive black holes openParSMBHsclosePar comma allow us to study the accretion history of the SMBH. Population synthesis models predict that comma at the peak of the global SMBH growth openParzvirgul1.5--3closePar comma nearly 50 % of all AGN should be Compton thick openParCTclosePar. Discovery of CT-AGN at high-redshift is still a challenging task. Here comma we propose to observe jointly with NuSTAR and XMM-Newton a bright CT-AGN candidate at redshift z=2.99 comma selected from the XMM serendipitous source catalog. The unabsorbed rest-frame 2-10 keV luminosity of the source is found to be Lxvirgul5e46 erg-s comma which potentially makes it the largest intrinsic luminosity quasar ever observed in X-rays comma and currently the only CT-AGN candidate that is observable by NuSTAR at z>virgul3.