mlir/test/Integration/data/test_symmetric.mtx

%%MatrixMarket matrix coordinate real symmetric
%
% This is a test sparse matrix in Matrix Market Exchange Format.
% see https://math.nist.gov/MatrixMarket
%
5 5 7
1 1 5.0
1 3 4.1
2 2 3.0
2 4 2.0
3 3 1.0
4 4 4.0
5 5 5.0