The ZT (figure of merit) is an apples-to-apples number for comparing one thermoelectric material set to another. Higher is better.
Bismuth Telluride is the standard and has been for decades. It has a ZT of about 1.3. There have been some breakthroughs to exceed that in a few spots, but with limitations. Most of its competitors still exceed a ZT of 1.
This publication’s material is less than 0.01. Not all that newsworthy, unless I’m missing something.