Looking for a chemical anchors fastened to the underside of the 300mm thick concrete slab. Fastener will be subjected to 5kN pull
For a 5 kN tension load into the soffit of a 300 mm slab, a good starting point is Hilti HIT-HY 200-A V3 with a HAS-U threaded rod. It is approved for overhead installation and cures quickly, which helps when working upside down. HIT-RE 500 V4 is an alternative if a longer working time or deeper embedment is needed.
For overhead installation, use a piston plug and a rod holder so the adhesive fills the hole properly and the rod stays in place while it cures.
The final size and embedment depend on whether the 5 kN is a design or characteristic load, the concrete class (and whether it is cracked), edge and spacing distances, and any fire requirement. Run it in PROFIS Engineering, or contact MOZAECC.ZATeam@hilti.com, to confirm the design.