Eu tenho a solução. Aqui está:
SETLOCAL EnableDelayedExpansion
set tes=0
set name=
set path=
for /r %%h in (*.*) do (
IF !tes! LSS %%~zh (
SET tes= %%~zh
SET name= %%~nh
SET path= %%~ph
)
)
echo name = !name! >> Biggest.txt
echo size = !tes! >> Biggest.txt
echo path = !path! >> Biggest.txt