Try PNAS papers in section Mathematics (returns 2308 results, but some are cross-discipinary). In the early days there were a lot of pure mathematics papers listed under just 'Mathematics' (e.g. Hardy-Littlewood!). But these days they seem to be listed under Mathematics and Physical Sciences, for instance Morrison-Walker, Griffin-Ono-Rolen and Conway-Jiao-Torquato (actually Ken Ono seems to have published a bunch of stuff there...). This search however picks up a lot of stuff that you wanted to rule out, "use of (sophisticated) mathematical techniques to solve a scientific problem from another discipline."