Re: PVC to Clay Tile
Stainless steel band couplers are used underground all the time.
It will be below grade with direct contact to soil, so I don't thing a banded coupling will hold up very well
Have you checked the integrity of that vertical clay pipe further down?
It's quite common for them to crack or outright break. If so then you are risking more issues than any benifit.
Personally , i would remove that type of connection all together and run the downspouts above ground away from the house foundation.
"" an ounce of perception -- a pound of obscure "