/usr/lib/slepcdir/3.7.3/x86_64-linux-gnu-complex/lib/libslepc_complex.so.3.7 is in libslepc-complex-3.7.3-dev 3.7.3+dfsg1-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/slepcdir/3.7.3/x86_64-linux-gnu-complex/lib/libslepc_complex.so.3.7.3