Imo you only need 4 European stocks to play the AI infrastructure buildout. Save this post! $ATS.VI $IQE $SOI.PA $AMS.SW Everyone's crowded into the US names. These 4 sit at chokepoints most people often overlook at. Here's where each one fits and why it's hard to replace 1. $ATS.VI, AT&S (Austria): the board every AI chip sits on > AT&S makes IC substrates, the thin multilayer boards every AI accelerator is mounted on. No substrate, no GPU. Kulim plant 1 in Malaysia runs at full tilt for AMD, and Marvell was named the second anchor customer for Kulim plant 2. Substrates are now 63% of revenue and grew 93% cc last quarter, with substrate EBITDA margin at 42.3% vs 13.0% a year earlier > Why it's unique: NVIDIA just reserved capacity at Ibiden, SEMCO and Unimicron and committed to raising substrate capacity 2.5x. That leaves AMD, Marvell and every custom chip team competing for what's left, and AT&S is one of the few Western makers at scale. Customers are literally funding its plants. Goldman sees substrate demand beating supply by 34% in 2027 > And it's the cheapest of the lot. AT&S trades at 16.4x trailing EBITDA and 9.1x the FY26/27 guide midpoint. Every listed peer is at 37x to 58x, with Unimicron at 58x and Ibiden at 44.8x. Same product, same shortage, less than half the multiple 2. $IQE, IQE (UK): the scarcest material in AI optics > Inside AI optics the scarcest input is indium phosphide. IQE grows the epi wafers that lasers and photodetectors are built on, and it's the largest Western merchant epi maker. Lumentum went from 25-30% short in March to sold out to early 2029 this month. Photonics is now 60% of IQE's revenue, H1 sales were up 43% to £64.6m, and photonics segment margin almost doubled from 13.4% to 24.7%. MACOM put in £30m of equity plus a £15m note, and Tower signed a multi-year InP deal > Why it's unique: it's a merchant, so it sells to everyone instead of hoarding for its own lasers, and it runs every compound material at scale. It's mid-conversion of tools from GaAs to InP, which moves £15-25m of FY27 revenue onto InP economics. Yet the stock is down ~36% from its Oct 6 peak with no bad IQE news, a director just bought 500k shares at 39.13p, and it trades at 3.3x FY27 EV/sales vs 26x for LandMark 3. $SOI.PA, Soitec (France): the wafer behind every AI light link > Every silicon photonics chip, pluggable or co-packaged, is built on a silicon-on-insulator wafer. Soitec makes them with its Smart Cut process, and its photonics revenue is guided at 2.5 to 3x last year. GlobalFoundries calls it its "primary" 300mm supplier and it's qualified at TSMC and Tower > Why it's unique: UBS and BofA put its share of photonics SOI at ~95%. It doesn't have to bet on which optics architecture wins, because all of them start on the same wafer. The capacity is already built and paid for, with fab loading under 60% and no new fab needed until ~2029. More than 10 photonics customers have signed capacity reservations with deposits 4. $AMS.SW, ams OSRAM (Austria/Switzerland): the next short-reach link > This is the optionality pick. Copper runs out at ~2m and pluggables are expensive and power-hungry. The next thing is "wide and slow" links: hundreds of slow lanes using microLEDs or microVCSELs, being standardised at OCP. ams already makes 4 of the 7 building blocks, and it showed 32 Gb/s per lane at ~0.25 pJ/bit with no failures after 2,000+ hours of stress testing > Why it's unique: very few companies make both emitter types plus the photodiodes and the CMOS underneath in their own fab. Its EVIYOS car headlamp chips have bonded arrays to drivers in volume since 2023, which is the hardest step. To be clear, there's no AI order yet. But the core business is cheap at ~6.4x next year's EBITDA, so you're mostly getting the option for free The common thread: substrates, InP epi, photonics wafers and optical links. AI isn't limited by demand, it's limited by physical inputs, and Europe quietly owns a few of them Full deep dives on all 4, with scenarios, price lines and catalysts, are up for subscribers on lekiresearch.com. IQE's was just refreshed today.