  The nontrivial band structure of semimetals has attracted substantial
research attention in condensed matter physics and materials science in recent
years owing to its intriguing physical properties. Within this class, a group
of non-trivial materials known as nodal-line semimetals is particularly
important. Nodal-line semimetals exhibit the potential effects of electronic
correlation in nonmagnetic materials, whereas they enhance the contribution of
the Berry curvature in magnetic materials, resulting in high anomalous Hall
conductivity (AHC). In this study, two ferromagnetic compounds, namely ZrMnP
and HfMnP, are selected, wherein the abundance of mirror planes in the crystal
structure ensures gapped nodal lines at the Fermi energy. These nodal lines
result in one of the largest AHC values of 2840 ohm^-1cm^-1, with a high
anomalous Hall angle of 13.6 % in these compounds. First-principles
calculations provide a clear and detailed understanding of nodal line-enhanced
AHC. Our finding suggests a guideline for searching large AHC compounds.
