This question is basically a modification of this.
It's well known that Osmium is the densest material you can find at room temperature and pressure. I am curious at higher pressures (and lower temperature?) if any denser materials are known. Obviously if the pressure approaches that of a Neutron star's gravitational environment we would expect pure neutron star fluid to be of higher density. I am interested in pressures less than this. Ideally, pressure that can be achieved in a lab such as up to 770 gigapascals.
Have we found any materials in a lab which have a higher density than osmium at colder and higher pressure environment than ambient conditions?