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We report the magnetic and electronic transport properties of the inversion and time-reversal symmetry breaking Weyl semimetal NdAlGe. This material is analogous to NdAlSi, whose helical magnetism presents a rare example of a Weyl-mediated collective phenomenon, but with a larger spin-orbit coupling. Our neutron diffraction experiments revealed that NdAlGe, similar to NdAlSi, supports an incommensurate Ising spin density wave ($T_{\text{inc}}=6.8$ K) with a small helical spin canting of 3$^\circ$ and a long-wavelength of $\sim$ 35 nm, which transitions to a commensurate ferrimagnetic state below $T_{\text{com}}=5.1$ K. Using small-angle neutron scattering, we showed that the zero-field cooled ferrimagnetic domains form stripes in real space with characteristic length scales of 18 nm and 72 nm parallel and perpendicular to the [110] direction, respectively. Interestingly, for the transport properties, NdAlSi does not exhibit an anomalous Hall effect (AHE) that is commonly observed in magnetic Weyl semimetals. In contrast to NdAlSi, we identify two different AHE regimes in NdAlGe that are respectively governed by intrinsic Berry curvature and extrinsic disorders/spin fluctuations. Our study suggests that Weyl-mediated magnetism prevails in this group of noncentrosymmetric magnetic Weyl semimetals NdAl$X$, but transport properties including AHE are affected by material-specific extrinsic effects such as disorders, despite the presence of prominent Berry curvature., Preprint, 16 pages, 6 main figures, 6 supplementary figures

The Dzyaloshinskii-Moriya (DM) interaction is present in the transition metal dichalcogenides (TMDC) magnets of form ${M}_{1/3}T{\mathrm{S}}_{2}$ ($M=3d$ transition metal, $T\ensuremath{\in}{\mathrm{Nb},\mathrm{Ta}}$), given that the intercalants $M$ form $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ superlattices within the structure of the parent materials $T{\mathrm{S}}_{2}$ and break the centrosymmetry. Competition between DM and ferromagnetic exchange interactions has been shown to stabilize a topological defect known as a chiral soliton in select intercalated TMDCs, initiating interest both in terms of fundamental physics and the potential for technological applications. In the current article we report on our study of the materials ${\mathrm{V}}_{1/3}{\mathrm{TaS}}_{2}$ and ${\mathrm{V}}_{1/3}{\mathrm{NbS}}_{2}$, using a combination of x-ray powder diffraction, magnetization, and single crystal neutron diffraction. Historically identified as ferromagnets, our diffraction results instead reveal that vanadium spins in these compounds are arranged into an A-type antiferromagnetic configuration at low temperatures. Refined moments are 1.37(6) and 1.50(9) ${\ensuremath{\mu}}_{B}$ for ${\mathrm{V}}_{1/3}{\mathrm{TaS}}_{2}$ and ${\mathrm{V}}_{1/3}{\mathrm{NbS}}_{2}$, respectively. Transition temperatures ${T}_{c}=32\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ for ${\mathrm{V}}_{1/3}{\mathrm{TaS}}_{2}$ and 50 K for ${\mathrm{V}}_{1/3}{\mathrm{NbS}}_{2}$ are obtained from the magnetization and neutron diffraction results. We attribute the small net magnetization observed in the low-temperature phases to a subtle ($\ensuremath{\sim}{2}^{\ensuremath{\circ}}$) canting of XY spins in the out-of-plane direction. These new results are indicative of dominant antiferromagnetic exchange interactions between the vanadium moments in adjacent $ab$ planes, likely eliminating the possibility of identifying stable chiral solitons in the current materials.