Investigations of
reaction mixtures RE
x
(Au
0.79
Si
0.21
)
100–
x
(RE =
Y and Gd) yielded the compounds REAu
3
Si which
adopt a new structure type, referred to as GdAu
3
Si structure
(
tP
80,
P
4
2
/
mnm
,
Z
= 16,
a
= 12.8244(6)/12.7702(2)
Å, and
c
= 9.0883(8)/9.0456(2) Å for GdAu
3
Si/YAu
3
Si, respectively). REAu
3
Si was
afforded as millimeter-sized faceted crystal specimens from solution
growth employing melts with composition RE
18
(Au
0.79
Si
0.21
)
82
. In the GdAu
3
Si structure,
the Au and Si atoms are strictly ordered and form a framework built
of corner-connected, Si-centered, trigonal prismatic units SiAu
6
. RE atoms distribute on 3 crystallographically different
sites and each attain a 16-atom coordination by 12 Au and 4 Si atoms.
These 16-atom polyhedra commonly fill the space of the unit cell.
The physical properties of REAu
3
Si were investigated by
heat capacity, electrical resistivity, and magnetometry techniques
and are discussed in the light of theoretical predictions. YAu
3
Si exhibits superconductivity around 1 K, whereas GdAu
3
Si shows a complex magnetic ordering, likely related to frustrated
antiferromagnets exhibiting chiral spin textures. GdAu
3
Si-type phases with interesting magnetic and transport properties
may exist in an extended range of ternary RE–Au–Si systems,
similar to the compositionally adjacent cubic 1/1 approximants RE(Au,Si)
∼6
.