  The family of group IV-VI monochalcogenides has an atomically puckered
layered structure, and their atomic bond configuration suggests the possibility
for the realization of various polymorphs. Here, we report the synthesis of the
first hexagonal polymorph from the family of group IV-VI monochalcogenides,
which is conventionally orthorhombic. Recently predicted four-atomic-thick
hexagonal GeSe, so-called {\gamma}-GeSe, is synthesized and clearly identified
by complementary structural characterizations, including elemental analysis,
electron diffraction, high-resolution transmission electron microscopy imaging,
and polarized Raman spectroscopy. The electrical and optical measurements
indicate that synthesized {\gamma}-GeSe exhibits high electrical conductivity
of 3x10^5 S/m, which is comparable to those of other two-dimensional layered
semimetallic crystals. Moreover, {\gamma}-GeSe can be directly grown on h-BN
substrates, demonstrating a bottom-up approach for constructing vertical van
der Waals heterostructures incorporating {\gamma}-GeSe. The newly identified
crystal symmetry of {\gamma}-GeSe warrants further studies on various physical
properties of {\gamma}-GeSe.
