Andrei Tarkovsky's films were not all in the science-fiction genre, but they do all share a kind of deliberate, meditative pace, first as a means to draw from the viewer's deeper consciousness and secondly for the purpose of boring Soviet film censors who were not especially attuned to the nuances of high art.
I haven't seen "Stalker" and "Zerkalo" before now. "Solaris" I've seen a few times already because it's the kind of experience that grows on the viewer, as we say. Many may prefer the greatly shortened 2002 remake by Steven Soderburgh, but the original is a substantially different experience. With great appreciation for Google Video, I share these with you now.
Zerkalo(The Mirror) (1975)