Fig. 1
From: Multi-loop node line states in ternary MgSrSi-type crystals

Possible NL structures in BZ. a The m-NL protected by mirror symmetry (left) and the s-NL protected by symmetry S=PT (right). b A pair of touched m-NLs associated with two vertical mirror planes. The small spheres located at the touching points of two NLs are also dubbed as “nexus points”. c A pair of separated, touched and crossed s-NLs depending on their distance in the BZ. d A pair of touched s-NL and m-NL. Except the nexus point O, the s-NL also penetrates the invariant plane of the m-NL through another isolated point marked as E