Emergent phases often appear when the electronic kinetic energy is comparable to the Coulomb interactions. One approach to seek material systems as hosts of such emergent phases is to realize localization of electronic wavefunctions due to the geometric frustration inherent in the crystal structure, resulting in flat electronic bands. Recently, such efforts have found a wide range of exotic phases in the two-dimensional kagome lattice, including magnetic order, time-reversal symmetry breaking charge order, nematicity, and superconductivity. However, the interlayer coupling of the kagome layers disrupts the destructive interference needed to completely quench the kinetic energy. Here we demonstrate that an interwoven kagome network—a pyrochlore lattice—can host a three dimensional (3D) localization of electron wavefunctions. Meanwhile, the nonsymmorphic symmetry of the pyrochlore lattice guarantees all band crossings at the Brillouin zone X point to be 3D gapless Dirac points, which was predicted theoretically but never yet observed experimentally. Through a combination of angle-resolved photoemission spectroscopy, fundamental lattice model and density functional theory calculations, we investigate the novel electronic structure of a Laves phase superconductor with a pyrochlore sublattice, CeRu₂. We observe evidence of flat bands originating from the Ce 4f orbitals as well as flat bands from the 3D destructive interference of the Ru 4d orbitals. We further observe the nonsymmorphic symmetry-protected 3D gapless Dirac cone at the X point. Our work establishes the pyrochlore structure as a promising lattice platform to realize and tune novel emergent phases intertwining topology and many-body interactions.

当电子动能与库仑相互作用相当时，通常会出现突现相。寻找材料系统作为此类涌现相的宿主的一种方法是由于晶体结构中固有的几何挫败而实现电子波函数的局域化，从而产生平坦的电子带。最近，这些努力在二维戈薇晶格中发现了各种各样的奇异相，包括磁序、时间反转对称性破缺电荷序、向列性和超导性。然而，戈薇层的层间耦合破坏了完全淬灭动能所需的相消干涉。在这里，我们证明了交织的 kagome 网络（烧绿石晶格）可以承载电子波函数的三维 (3D) 局域化。同时，烧绿石晶格的非对称对称性保证了布里渊区X点处的所有能带交叉都是3D无间隙狄拉克点，这是理论上预测的，但尚未在实验中观察到。通过结合角分辨光电子能谱、基本晶格模型和密度泛函理论计算，我们研究了具有烧绿石亚晶格的拉夫斯相超导体CeRu ₂的新型电子结构。我们观察到来自 Ce 4 f轨道的平带以及来自 Ru 4 d轨道的 3D 相消干涉的平带的证据。我们进一步观察 X 点处的非对称对称保护的 3D 无间隙狄拉克锥。我们的工作将烧绿石结构建立为一个有前途的晶格平台，以实现和调整新颖的涌现相交织的拓扑和多体相互作用。