  Topological quantum materials represent a new class of matter with both
exotic physical phenomena and novel application potentials. Many Heusler
compounds, which exhibit rich emergent properties such as unusual magnetism,
superconductivity and heavy fermion behaviour, have been predicted to host
non-trivial topological electronic structures. The coexistence of topological
order and other unusual properties makes Heusler materials ideal platform to
search for new topological quantum phases (such as quantum anomalous Hall
insulator and topological superconductor). By carrying out angle-resolved
photoemission spectroscopy (ARPES) and ab initio calculations on rare-earth
half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observed the unusual
topological surface states on these materials, establishing them as first
members with non-trivial topological electronic structure in this class of
materials. Moreover, as LnPtBi compounds are non-centrosymmetric
superconductors, our discovery further highlights them as promising candidates
of topological superconductors.
