Merge files in R and write to SPSS .SAV file

I have a two datasets that are too large to open in SPSS. I have split the files into two subfiles for each. The task is to read these pairs of files into R, merge the two subfiles, and write the merged file to an SPSS .SAV file. https://docs.google.com/document/d/1-FSZQRhuuJmepMnaNi3u6dlfGu-rNWUqnZ0MYn_JB04/edit?usp=sharing
Confirm that the file can be opened in SPSS.