We have established that , although MnAlGe is not a van der Waals compound , due to the large separation between the magnetic square net layers of Mn atoms , the AHE is dominated by the 2D electronic features in the band structure . There are three important points we would like to emphasize . First , the electronic states near the Fermi energy were dominated by Mn - d orbitals , while the s and p orbitals of the nonmagnetic Al - Ge subunit only contributed far from the Fermi energy . The fat bands observed in Figure S2 , Supporting Information , clearly show the relative contribution of the orbitals in the band structure . Hence , the transport properties of MnAlGe were entirely determined by the Mn - square net layers . Second , the unique 2D distribution of the Berry curvature in MnAlGe that arose from the band anti - crossing of the nodal line perfectly matched the 2D FS obtained from the band constituting the nodal line . Therefore , the AHE observed in this compound originated from the 2D feature of the bands that contained nodal lines . Moreover , the scaling of ρ yx A versus xx ρ 2 indicates www.advmat.de www.advancedsciencenews.com the intrinsic contribution to AHE . It should be noted that the relation of ρ yx A versus xx ρ 2 is not strictly linear in the temperature dependent AHE data . Therefore , a temperature range 2 - 100 K has been used for linear fitting to obtain the intercept ≈560 S cm -1 as the intrinsic contribution ( see discussion in Supporting Information for the departure from linearity , Figure S17 , Supporting Information ) . Based on the ARPES study , the nodal - line anticrossings was situated just below the Fermi energy that enhanced the AHC . This can be understood from Figure 2f , which shows that shifting the nodal line from above to below the E F moves AHC from the base of a peak in the σ xy A versus E data to almost the peak . This explains the observation of a large AHC in experiments compared to the value predicted by DFT , when the Fermi energy is placed below the nodal line . Finally , the part of the FS that contributed the majority of the charge carriers for conduction exhibited dispersion in all three dimensions . Thus , the electrical resistivity and the ordinary Hall effect will demonstrate a small anisotropy , which is consistent with experimental observations . Next , we discuss how MnAlGe compares with other well - known 2D , FM , anomalous Hall systems . Quasi-2D kagome lattice compounds Co 3 Sn 2 S 2 and Fe 3 Sn 2 have recently been established as topological Weyl and massive Dirac semimetals . Interestingly , the separation between the Mn layers in MnAlGe ( 5.93 Å ) was larger than the separation between the two Co - kagome layers in Co 3 Sn 2 S 2 ( 4.39 Å ) and comparable to that of the Fe - kagome layers in Fe 3 Sn 2 ( 6.60 Å ) . Notably , while the FS in Fe 3 Sn 2 is open and quasi-2D , the FSs in Co 3 Sn 2 S 2 are 3D. The value of the AHC in MnAlGe was higher than in Fe 3 Sn 2 ( 170 S cm −1 ) and comparable to that of Co 3 Sn 2 S 2 ( 505 - 1130 S cm −1 ) . In a true , van der Waals , topological nodalline , compound Fe 3 GeTe 2 , the separation between the two magnetic layers was significantly larger ( 8.16 Å ) , while in Fe 1/4 TaS 2 , which forms by the Fe intercalation of the van der Waals gap of TaS 2 , the separation between the Fe layers ( 6.07 Å ) was approximately equal to MnAlGe . Importantly , the AHC and FM transition temperature of MnAlGe were among the highest reported , as shown in Table S2 , Supporting Information .