Over-large JPG files on export

I have a couple of files that export to very large JPG files directly from Lightroom - the same image imported into Photoshop and saved as a TIF exports to the expected size. For example direct export of the edited RAW file gives 3.18 MB for a 1200 by 1200 JPG an export of the TIF version is 1.34 MB. No changes were made in Photoshop other than saving as a TIF. The RAW and TIF files are 3823 pixels square