Abstract

Luminous quasars at z>4 provide key insights into the early Universe. Their rarity necessitates wide-field multiband surveys to efficiently separate them from the main astrophysical contaminants (i.e., ultracool dwarfs). To expand the sample of high-z quasars, we conducted targeted selections using optical, infrared, and radio surveys, which we complemented by literature-based quasar candidate catalogs. We report the discovery of 25 new quasars at 4.66.5 quasars we selected, but whose independent discovery has already been published in the literature. Three of the newly discovered quasars are strong radio emitters (L1.4a GHz = 0.09-1.0×1034a erga s-1a Hz-1). One source at z = 4.71 exhibits typical blazar-like properties, including a flat radio spectrum, a radio loudness of ~1000, and multifrequency variability. It was also detected by SRG/eROSITA X-ray telescope (f0.2-2.3a keV~1.3×10-13a erga s-1a cm-2). In addition, for seven 6.36 quasars reported in the literature. A z = 6.3 quasar exhibits a velocity difference of approximately 9000a kma s-1 between the Ca IV and Mga II emission lines. This means that it is one of the most extreme Ca IV outflows currently known. The sample also includes three high-ionization broad absorption line (HiBAL) quasars. One of these quasars shows potential evidence of an extremely fast outflow feature that reaches 47a 000a kma s-1. © The Authors 2025.