  We search for extra-tidal stars around two metal-poor Galactic globular
clusters, M53 and NGC 5053, using the near-infrared APOGEE spectra. Applying
the t-SNE algorithm on the chemical abundances and radial velocities results in
identification of two isolated stellar groups composed of cluster member stars
in the t-SNE projection plane. With additional selection criteria of radial
velocity, location in the color-magnitude diagram, and abundances from a manual
chemical analysis, we find a total of 73 cluster member candidates; seven
extra-tidal stars are found beyond the tidal radii of the two clusters. The
extra-tidal stars around the clusters tend to be located along the leading
direction of the cluster proper motion, and the individual proper motion of
these stars also seems to be compatible to those of clusters. Interestingly, we
find that one extra-tidal star of NGC 5053 is located on the southern outskirts
of M53, which is part of common stellar envelope by the tidal interaction
between two clusters. We discuss the nature of this star in the context of the
tidal interaction between two clusters. We find apparent Mg-Al anticorrelations
with a clear gap and spread ($\sim$0.9 dex) in Al abundances for both clusters,
and a light Si abundance spread ($\sim$0.3 dex) for NGC 5053. Since all
extra-tidal stars have Mg enhanced and Al depleted features, they could be
first-generation stars of two globular clusters. Our results support that M53
and NGC 5053 originated in dwarf galaxies and are surrounded by extended
stellar substructures of more numerous populations of clusters.
