Les Productions Zvon has released Memory Collection 05 - Sci-Fi and Aliens, which features samples from 10 Public Domain science fiction movies for a total of 1,750 WAV-format samples and a size of 1.44 GB. There's a free preview of 120 samples.
The films are from the 1930s to the 1970s covering different styles of soundtracks. Their soundtracks featured early electronic music with a creative mix of various types of sound sources.
The samples include voice/spoken word/dialogs, sfx/foley and music. Most of them can be further divided so you can have some fun yourself.
Like the first four packs, it is donationware with a minimum required donation of $20 (a bundle of the packs 01, 02, 03 and 05 is also available).
More info and download the free preview at: lesproductionszvon.com/Memory_Collection