# d‑Electron Heavy Fermion Behavior in a Near-Room-Temperature Polar Metallic Ferrimagnet: A Case of Mn5SiC

## TL;DR

Mn5SiC is a polar metallic ferrimagnet with heavy Fermion behavior near room temperature, showing unique electronic and magnetic properties.

## Contribution

Discovery of d-electron heavy Fermion behavior in a near-room-temperature polar metallic ferrimagnet.

## Key findings

- Mn5SiC exhibits ferrimagnetic ordering with a transition temperature of 284 K.
- The material shows a large Kadowaki–Woods ratio and a many-body renormalization factor of 5.5, indicating heavy Fermion behavior.
- Crystal structure and magnetic properties were confirmed using diffraction and theoretical calculations.

## Abstract

Polycrystalline Mn5SiC was synthesized by
using a high-temperature
solid-state method. Mn5SiC adopts a polar space group (Cmc21) with six crystallographic Mn sites confirmed
by X-ray and neutron diffraction, transmission electron microscopy,
and second harmonic generation experiments. The complex crystal structure
features edge-sharing trigonal prisms and icosahedra, as well as face/edge-sharing
pentagonal prisms. Magnetic measurements indicate ferrimagnetic ordering
with a transition temperature of 284 K. The ferrimagnetic structure
(magnetic space group Cm’c’21) was further identified by powder neutron diffraction, where collinear
Mn spins align along the crystallographic c-axis.
The refined magnetic moment for each crystallographic Mn site at 4
K is 1.8(2), −2.42(9), −1.72(8), 0.51(6), 0.50(4), and
1.7(2) μB. Density functional theory calculations
confirm both the metallic behavior and the ferrimagnetic structure
observed experimentally and further provide insight into the observed
Mn moment dependence across crystallographic sites. The resistivity
and specific heat measurements and density functional theory calculations
reveal a substantially large Kadowaki–Woods ratio of 5 ×
10–5 μΩ·cm/(mJ/mol)2 and a many-body renormalization factor of 5.5, indicating the unusual
heavy Fermion behavior in such an itinerant magnetic metal.