  Vertical integration of two-dimensional (2D) van der Waals (vdW) materials
with different quantum ground states is predicted to lead to novel electronic
properties that are not found in the constituent layers. Here, we present the
direct synthesis of superconductor-magnet hybrid heterostructures by combining
superconducting niobium diselenide (NbSe$_2$) with the monolayer (ML) vanadium
diselenide (VSe$_2$). More significantly, the in-situ growth in ultra-high
vacuum (UHV) allows to produce a clean and an atomically sharp interfaces.
Combining different characterization techniques and density-functional theory
(DFT) calculations, we investigate the electronic and magnetic properties of
VSe$_2$ on NbSe$_2$. Low temperature scanning tunneling microscopy (STM)
measurements demonstrate a reduction of the superconducting gap on VSe$_2$
layer. This together with the lack of charge density wave signatures indicates
magnetization of the sheet, but not of a conventional itinerant ferromagnet.
