Fabrication of new types of superconductors with novel physical properties
has always been a major thread in the research of superconducting materials. An
example is the enormous interests generated by the cascade of correlated
topological quantum states in the newly discovered vanadium-based kagome
superconductors AV3Sb5 (A=K, Rb, and Cs) with a Z2 topological band structure.
Here we report the successful fabrication of single-crystals of titanium-based
kagome metal CsTi3Bi5 and the observation of superconductivity and electronic
nematicity. The onset of the superconducting transition temperature Tc is
around 4.8 K. In sharp contrast to the charge density wave superconductor
AV3Sb5, we find that the kagome superconductor CsTi3Bi5 preserves translation
symmetry, but breaks rotational symmetry and exhibits an electronic nematicity.
The angular-dependent magnetoresistivity shows a remarkable two-fold rotational
symmetry as the magnetic field rotates in the kagome plane. The scanning
tunneling microscopy and spectroscopic imaging detect rotational-symmetry
breaking C2 quasiparticle interference patterns (QPI) at low energies,
providing further microscopic evidence for electronic nematicity. Combined with
first-principle calculations, we find that the nematic QPI is orbital-selective
and dominated by the Ti dxz and dyz orbitals, possibly originating from the
intriguing orbital bond nematic order. Our findings in the new "135" material
CsTi3Bi5 provide new directions for exploring the multi-orbital correlation
effect and the role of orbital or bond order in the electron liquid crystal
phases evidenced by the symmetry breaking states in kagome superconductors