The evolution of electronic transport under external tuning is a key aspect of quantum materials research. This thesis investigates how resistivity and related transport properties are governed by structural, electronic, and magnetic interactions, using layered pnictide compounds as a unified platform. Despite similar crystallographic frameworks, the selected materials (BaNi2P2, BaMn2P2, and EuIn2P2) exhibit distinct ground states, enabling a comparative study of how pressure and magnetic field affect superconductivity, metal-insulator transitions, and anomalous scattering.

We first study the pressure dependence of the superconducting transition temperature in BaNi2P2, a superconductor structurally related to iron-based systems. By comparing resistivity measurements with Migdal-Eliashberg calculations, we show that Tc follows conventional BCS behavior, indicating that Ni-based BaNi2P2 forms a distinct class from Fe-based counterparts.

In the antiferromagnetic insulator BaMn2P2, we report a pressure-induced insulator-to-metal transition. At ambient pressure, resistivity shows two-gap thermally activated behavior, with activation energies confirmed by angle-resolved photoemission spectroscopy (ARPES). Under pressure, resistivity drops sharply, and metallic behavior emerges above 7 GPa. DFT+U calculations confirm the gap closing, and X-ray diffraction shows that the transition coincides with a critical unit cell volume, indicating coupling between structure and bandwidth.

EuIn2P2, a ferromagnetic semimetal, exhibits a sharp resistivity peak near its magnetic ordering temperature. This anomaly, unaccompanied by structural changes or gap formation, originates from magnetic scattering, supported by magnetoresistance, anomalous Hall effect, magnetic susceptibility, and specific heat data. Although pressure shifts the peak position, its shape remains unchanged, making the anomaly especially intriguing.

To explain this behavior, we develop a general model for resistivity arising from scattering by fluctuating magnetic moments. The model relates scattering time to the magnetic structure factor S(q) and applies to arbitrary energy dispersions and correlation functions. A resistivity peak arises when the inverse correlation length 1/xi becomes comparable to the Fermi momentum kF. The peak height scales inversely with kF^(d+2), where d is the system dimensionality, showing the effect is strongest in low-dimensional systems with small Fermi surfaces.

We apply this model to EuIn2P2 using parameters from ARPES and classical Monte Carlo simulations. The calculated resistivity reproduces the anomalous peak at Tc ~ 24 K and its suppression under magnetic field, in excellent agreement with experiments. This confirms short-range magnetic correlations as the dominant scattering mechanism and illustrates the model's applicability to real materials.

Overall, these results show how resistivity and electron scattering serve as powerful probes of physical phenomena in structurally related pnictides. The three case studies demonstrate that resistivity, interpreted alongside complementary measurements and theory, reveals the electronic, structural, and magnetic mechanisms governing transport. This work shows that simple measurements, placed within a suitable framework, offer deep insights into complex correlated electron systems and lay the groundwork for future research in quantum materials.