/usr/lib/slepcdir/3.7.4/x86_64-linux-gnu-real/lib/libslepc_real.so.3.7.4 is in libslepc3.7.4-dev 3.7.4+dfsg1-2build8.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/slepcdir/3.7.4/x86_64-linux-gnu-real/lib/../../../../x86_64-linux-gnu/libslepc_real.so.3.7.4