* German DAX and Swiss SMI equity indexes underperform
* FTSEurofirst 300 flat
* Some relief over BES rescue deal
* But euro zone Sentix index fell in August
By Sudip Kar-Gupta
LONDON, Aug 4 (Reuters) - The German and Swiss stock markets were the worst performers in Europe on Monday, as the impact of sanctions against Russia pegged back equities and offset some relief over a rescue deal for Banco Espirito Santo (BES) .
Sentix's August survey of euro zone sentiment showed an unexpected slump in the previous month as new EU sanctions on Russia weighed on growth expectations, particularly in Europe's largest economy Germany, which has a large exposure to Russia.
Sportswear company Adidas issued a profit warning last week, blaming its exposure to a weak Russian market, and brokerage Berenberg cut its rating to "hold" from "buy".
"Germany stands to lose more than most in case of additional sanctions against Russia," said SteppenWolf Capital chief investment officer Phoebus Theologites.
Germany's benchmark DAX index, which had hit a record high of 10,050.98 points in late June, was down by 0.3 percent at 9,183.07 points - underperforming the broader pan-European FTSEurofirst 300 index which was flat.
Switzerland's benchmark SMI index fell 0.9 percent, with shares in the country's two biggest banks - UBS and Credit Suisse - hovering near their lowest levels in about a year.
Traders said the banks were suffering from a continuation of negative momentum from last week, when the Zurich stock exchange was closed for a public holiday on Friday.
Regulators have been investigating trading units of both over the last year as well as looking into tax evasion allegations.
Switzerland effectively ended its banking secrecy in May by agreeing to join other countries in sharing tax information, once a standard method of sharing is agreed.
"Switzerland has abandoned its banks. The banks are going to struggle," said Theologites.
However, there was some relief for the banking sector after Portugal agreed to spend 4.9 billion euros on rescuing BES, its largest listed bank. The deal comes just months after the country exited an international bailout.
While BES shares - which plunged 73 percent last week - were still suspended, shares in Portugal's second-largest listed bank Millennium bcp rose 3.9 percent while Lisbon's PSI-20 equity index edged up 0.2 percent.
"The market's initial reaction is that it's pretty reassuring to see Portugal moving quickly to rescue BES. We don't have all the details, but overall it eases systemic fears that had resurfaced last week," Saxo Bank sales trader Andrea Tueni said.
"But it's not enough to spark a real rebound in the overall market. This is mostly a technical bounce from last week's slide and the trend remains negative for now," Tueni said. (U.S. dollar = 0.7451 euros)
Europe bourses in 2014: link.reuters.com/pap87v
Asset performance in 2014: link.reuters.com/gap87v
Today's European research round-up (Additional reporting by Blaise Robinson; Editing by Louise Ireland)