The 3 sonatas of Hindemith could be something 20th century and atonal you want to explore.
Anatoly Alexandrov (1888-1962) was a significant pre-Revolutionary Russian composer whose lineage stems from Rachmaninov, Medtner, and early Scriabin.
I think that you'll find that Alexandrov died in 1982, not 1962, his first piano sonata and first string quartet each date from 1914 and his cello sonata from 1981-82.Best,Alistair