Lah, PhilipOnken, ChristopherNorris, Ray PD'Eugenio, Francesco2024-08-302024-08-300035-8711https://hdl.handle.net/1885/733716057We take a sample of 94 ultraluminous, optical quasars from the search of over 14 486 deg2 by Onken et al. in the range 4.4 < redshift < 5.2 and match them against the Rapid ASKAP Continuum Survey (RACS) observed on the Australian Square Kilometre Array Pathfinder (ASKAP). From this most complete sample of the bright end of the redshift ∼5 quasar luminosity function, there are 10 radio continuum detections, of which eight are considered radio-loud quasars. The radio-loud fraction for this sample is 8.5 ± 2.9 per cent. Jiang et al. found that there is a decrease in the radio-loud fraction of quasars with increasing redshift and an increase with increasing absolute magnitude at rest frame 2500 Å. We show that the radio-loud fraction of our quasar sample is consistent with that predicted by Jiang et al.,extending their result to higher redshifts.CAO was supported by the Australian Research Council (ARC) through Discovery Project DP190100252. FDE acknowledges support by the Science and Technology Facilities Council (STFC), by the ERC through Advanced Grant 695671 ‘QUENCH’, and by the UKRI Frontier Research grant RISE and FALL. The national facility capability for SkyMapper has been funded through ARC LIEF grant LE130100104 from the Australian Research Council, awarded to the University of Sydney, the Australian National University, Swinburne University of Technology, the University of Queensland, the University of Western Australia, the University of Melbourne, Curtin University of Technology, Monash University, and the Australian Astronomical Observatoryapplication/pdfen-AU© 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Societygalaxies: quasars: generalradio continuum: galaxies202310.1093/mnras/stad26872024-04-28